Figure 1. Typical Flyback Application.
Product3
Adapter1Open
Frame2
Open
Frame2
OUTPUT POWER TABLE
Table 1.
Notes:
1. Typical continuous power in a non-ventilated enclosed adapter measured at
50 ˚C ambient.
2. Maximum practical continuous power in an open frame design with adequate
heat sinking, measured at 50 ˚C ambient. See key applications section for
detailed conditions.
3. Packages: P: DIP-8B, G: SMD-8B, Y: TO-220-7B.
PI-2503-062515
AC
IN
DC
OUT
D
S
C
TOPSwitch-FX
M
+
-
F
CONTROL
Product Highlights
Lower System Cost, High Design Flexibility
• Features eliminate or reduce cost of external components
• Fully integrated soft-start for minimum stress/overshoot
• Externally settable accurate current limit
• Wider duty cycle for more power, smaller input capacitor
• Line under-voltage (UV) detection: no turn off glitches
• Line overvoltage (OV) shutdown extends line surge limit
• Line feed-forward with maximum duty cycle (DCMAX)
reduction rejects ripple and limits DCMAX at high line
• Single resistor sets OV/UV thresholds, DCMAX reduction
• Frequency jittering reduces EMI and EMI filtering costs
• Regulates to zero load without dummy loading
• 132 kHz frequency reduces transformer/power supply size
• Half frequency option for video applications
• Hysteretic thermal shutdown for automatic recovery
• Large thermal hysteresis prevents PC board overheating
• Standard packages with omitted pins for large creepage
• Active-on and active-off remote ON/OFF capability
• Synchronizable to a lower frequency
EcoSmart™– Energy Efficient
• Cycle skipping reduces no-load consumption
• Reduced consumption in remote off mode
• Half frequency option for high efficiency standby
• Allows shutdown/wake-up via LAN/input port
Description
TOPSwitch™-FX uses the proven TOPSwitch topology and
cost effectively integrates many new functions that reduce
system cost and, at the same time, improve design flexibility,
performance and energy efficiency. Like TOPSwitch, the
high-voltage power MOSFET, PWM control, fault protection
and other control circuitry are all integrated onto a single
CMOS chip, but with two added terminals. The first one is a
MULTI-FUNCTION (M) pin, which implements programmable
line OV/UV shutdown and line feed-forward/DCMAX reduction
with line voltage. The same pin can be used instead to
externally set an accurate current limit. In either case, this pin
can also be used for remote ON/OFF or to synchronize the
oscillator to an external, lower frequency signal. The second
added terminal is the FREQUENCY (F) pin and is available only
in the Y package. This pin provides the half frequency option
when connected to CONTROL (C) instead of SOURCE (S).
The features on the new pins can be disabled by shorting
them to the SOURCE, which allows the device to operate in a
three terminal TOPSwitch mode, but with the following new
transparent features: soft-start, cycle skipping, 132 kHz
switching frequency, frequency jittering, wider DCMAX,
hysteretic thermal shutdown and larger creepage. In addition,
all critical parameters such as frequency, current limit, PWM
gain, etc. have tighter temperature and absolute tolerances
compared to the TOPSwitch-II family. Higher current limit
accuracy and larger DCMAX, when combined with other
features allow for a 10% to 15% higher power capability on the
TOPSwitch-FX devices compared to equivalent TOPSwitch-II
devices for the same input/output conditions.
TOP232P
TOP232G
TOP232Y
TOP233P
TOP233G
TOP233Y
TOP234P
TOP234G
TOP234Y
230 VAC ±15%
Adapter1
85-265 VAC
9 W 15 W 6.5 W 10 W
10 W 25 W 7 W 15 W
13 W 25 W 9 W 15 W
20 W 50 W 15 W 30 W
16 W 30 W 11 W 20 W
30 W 75 W 20 W 45 W
TOP232-234
TOPSwitch-FX Family
www.power.com June 2015
Design Flexible, EcoSmart, Integrated
Off-Line Switcher
This Product is Covered by Patents and/or Pending Patent Applications.
This product is not recommended for new designs.
Rev. C 06/15
2
TOP232-234
www.power.com
Section List
Pin Functional Description ....................................................................................................................................... 3
TOPSwitch-FX Family Functional Description ........................................................................................................ 4
CONTROL (C) Pin Operation .................................................................................................................................... 4
Oscillator and Switching Frequency .......................................................................................................................... 5
Pulse Width Modulator and Maximum Duty Cycle .................................................................................................... 5
Minimum Duty Cycle and Cycle Skipping ................................................................................................................. 6
Error Amplifier .......................................................................................................................................................... 6
On-chip Current Limit with External Programability ................................................................................................... 6
Line Undervoltage Detection (UV) ............................................................................................................................. 6
Line Overvoltage Shutdown (OV) .............................................................................................................................. 7
Line Feed-Forward with DCMAX Reduction ................................................................................................................ 7
Remote ON/OFF and Synchronization ...................................................................................................................... 7
Soft-Start ................................................................................................................................................................. 8
Shutdown/Auto-Restart ........................................................................................................................................... 8
Hysteretic Over-Temperature Protection ................................................................................................................... 8
Bandgap Reference ................................................................................................................................................. 8
High-Voltage Bias Current Source ............................................................................................................................ 8
Using FREQUENCY and MULTI-FUNCTION Pins .................................................................................................... 9
FREQUENCY (F) Pin Operation ................................................................................................................................ 9
MULTI-FUNCTION (M) Pin Operation ........................................................................................................................ 9
Typical Uses of FREQUENCY (F) Pin ...................................................................................................................... 11
Typical Uses of MULTI-FUNCTION (M) Pin ............................................................................................................. 12
Application Examples ............................................................................................................................................. 14
A High Efficiency, 30 W, Universal Input Power Supply ........................................................................................... 14
35 W Multiple Output Power Supply ....................................................................................................................... 15
17 W PC Standby Power Supply ........................................................................................................................... 16
Processor Controlled Supply Turn On/Off ............................................................................................................... 17
Key Application Considerations .............................................................................................................................. 19
TOPSwitch-FX vs. TOPSwitch-ll ............................................................................................................................. 19
TOPSwitch-FX Design Considerations ................................................................................................................... 20
TOPSwitch-FX Selection .................................................................................................................................. 20
Input Capacitor ................................................................................................................................................ 20
Primary Clamp and Output Reflected Voltage VOR .......................................................................................... 20
Output Diode ................................................................................................................................................... 21
Soft-Start ......................................................................................................................................................... 21
EMI ................................................................................................................................................................. 21
Transformer Design .......................................................................................................................................... 21
Standby Consumption ..................................................................................................................................... 23
TOPSwitch-FX Layout Considerations .................................................................................................................... 23
Primary Side Connections ............................................................................................................................... 23
Y-Capacitor ..................................................................................................................................................... 23
Heat Sinking .................................................................................................................................................... 23
Quick Design Checklist .......................................................................................................................................... 23
Design Tools .......................................................................................................................................................... 23
Product Specifications and Test Conditions .......................................................................................................... 24
Typical Performance Characteristics ..................................................................................................................... 30
Package Outlines .................................................................................................................................................... 34
Rev. C 06/15
3
TOP232-234
www.power.com
Figure 2. Functional Block Diagram.
Pin Functional Description
DRAIN (D) Pin:
High-voltage power MOSFET drain output. The internal
start-up bias current is drawn from this pin through a switched
high-voltage current source. Internal current limit sense point
for drain current.
CONTROL (C) Pin:
Error amplifier and feedback current input pin for duty cycle
control. Internal shunt regulator connection to provide internal
bias current during normal operation. It is also used as the
connection point for the supply bypass and auto-restart/
compensation capacitor.
MULTI-FUNCTION (M) Pin:
Input pin for OV, UV, line feed-forward with DCMAX reduction,
external set current limit, remote ON/OFF and synchronization.
A connection to SOURCE pin disables all functions on this pin
and makes TOPSwitch-FX operate in simple three terminal
mode (like TOPSwitch-II).
FREQUENCY (F) Pin: (Y package only)
Input pin for selecting switching frequency: 132 kHz if
connected to SOURCE pin and 66 kHz if connected to
CONTROL pin. The switching frequency is internally set for
132 kHz only operation in P and G packages.
Figure 3. Pin Configuration.
SOURCE (S) Pin:
Output MOSFET source connection for high-voltage power
return. Primary side control circuit common and reference
point.
PI-2535-062615
SHUTDOWN/
AUTO-RESTART
PWM
COMPARATOR
CLOCK
SAW
HALF
FREQUENCY
OSCILLATOR WITH JITTER
CONTROLLED
TURN-ON
GATE DRIVER
CURRENT LIMIT
COMPARATOR
INTERNAL UV
COMPARATOR
INTERNAL
SUPPLY
5.8 V
4.8 V
SOURCE (S)
S
R
Q
Q
DMAX
STOP SOFT-
START
-
+
CONTROL (C)
MULTI-
FUNCTION (M)
FREQUENCY (F)
(Y Package Only)
-
+
5.8 V
IFB
RE
ZC
VC
+
-
LEADING
EDGE
BLANKING
∏ 8
1
HYSTERETIC
THERMAL
SHUTDOWN
SHUNT REGULATOR/
ERROR AMPLIFIER
+
-
DRAIN (D)
ON/OFF
DCMAX
VBG
DCMAX
VBG + VT
0
OV/UV
VI (LIMIT)
CURRENT
LIMIT
ADJUST
LINE
SENSE
SOFT START
PI-2501-031901
Tab Internally
Connected to SOURCE Pin
Y Package (TO-220-7B)
P Package (DIP-8B)
G Package (SMD-8B)
CD
S
S
S
S
1 C
3 M
5 F
4 S
7 D
M8
5
7
1
4
2
3
Rev. C 06/15
4
TOP232-234
www.power.com
TOPSwitch-FX Family Functional Description
Figure 4. Relationship of Duty Cycle to CONTROL Pin Current.
PI-2504-072799
Duty Cycle (%)
I
C
(mA)
IM = 140 µA
IM = 190 µA
IM < IM(DC)
1.91.5 5.5 5.9
Slope = PWM Gain
I
CD1
I
B
Auto-restart
78
1.5
47
Like TOPSwitch, TOPSwitch-FX is an integrated switched
mode power supply chip that converts a current at the control
input to a duty cycle at the open drain output of a high-voltage
power MOSFET. During normal operation the duty cycle of the
power MOSFET decreases linearly with increasing CONTROL
pin current as shown in Figure 4.
In addition to the three terminal TOPSwitch features, such as
the high-voltage start-up, the cycle-by-cycle current limiting,
loop compensation circuitry, auto-restart, thermal shutdown,
etc., the TOPSwitch-FX incorporates many additional functions
that reduce system cost, increase power supply performance
and design flexibility. A patented high-voltage CMOS
technology allows both the high-voltage power MOSFET and
all the low voltage control circuitry to be cost effectively
integrated onto a single monolithic chip.
Two terminals, FREQUENCY (available only in Y package) and
MULTI-FUNCTION, have been added to implement some of
the new functions. These terminals can be connected to the
SOURCE pin to operate the TOPSwitch-FX in a TOPSwitch-
like three terminal mode. However, even in this three terminal
mode, the TOPSwitch-FX offers many new transparent
features that do not require any external components:
1. A fully integrated 10 ms soft-start reduces peak currents
and voltages during start-up and practically eliminates
output overshoot in most applications.
2. DCMAX of 78% allows smaller input storage capacitor, lower
input voltage requirement and/or higher power capability.
3. Cycle skipping at minimum pulse width achieves regulation
and very low power consumption at no load.
4. Higher switching frequency of 132 kHz reduces the
transformer size with no noticeable impact on EMI or on
high line efficiency.
5. Frequency jittering reduces EMI.
6. Hysteretic over-temperature shutdown ensures automatic
recovery from thermal fault. Large hysteresis prevents circuit
board overheating.
7. Packages with omitted pins and lead forming provide large
DRAIN creepage distance.
8. Tighter absolute tolerances and smaller temperature vari-
ations on switching frequency, current limit and PWM gain.
The MULTI-FUNCTION pin is usually used for line sensing by
connecting a resistor from this pin to the rectified DC high-
voltage bus to implement line over-voltage (OV)/under-voltage
(UV) and line feed-forward with DCMAX reduction. In this mode,
the value of the resistor determines the OV/UV thresholds and
the DCMAX is reduced linearly starting from a line voltage above
the under-voltage threshold. In high efficiency applications, this
pin can be used in the external current limit mode instead, to
reduce the current limit externally (to a value close to the
operating peak current), by connecting the pin to SOURCE
through a resistor. The same pin can also be used as a
remote ON/OFF and a synchronization input in both modes.
The FREQUENCY pin in the TO-220 package sets the
switching frequency to the default value of 132 kHz when
connected to SOURCE pin. A half frequency option can be
chosen by connecting this pin to CONTROL pin instead.
Leaving this pin open is not recommended.
CONTROL (C) Pin Operation
The CONTROL pin is a low impedance node that is capable of
receiving a combined supply and feedback current. During
normal operation, a shunt regulator is used to separate the
feedback signal from the supply current. CONTROL pin
voltage VC is the supply voltage for the control circuitry
including the MOSFET gate driver. An external bypass
capacitor closely connected between the CONTROL and
SOURCE pins is required to supply the instantaneous gate
drive current. The total amount of capacitance connected to
this pin also sets the auto-restart timing as well as control loop
compensation.
When rectified DC high-voltage is applied to the DRAIN pin
during start-up, the MOSFET is initially off, and the CONTROL
pin capacitor is charged through a switched high-voltage
current source connected internally between the DRAIN and
CONTROL pins. When the CONTROL pin voltage VC reaches
approximately 5.8 V, the control circuitry is activated and the
soft-start begins. The soft-start circuit gradually increases the
duty cycle of the MOSFET from zero to the maximum value
over approximately 10 ms. If no external feedback/supply
current is fed into the CONTROL pin by the end of the
soft-start, the high-voltage current source is turned off and the
CONTROL pin will start discharging in response to the supply
current drawn by the control circuitry. If the power supply is
designed properly, and no fault condition such as open loop or
shorted output exists, the feedback loop will close, providing
external CONTROL pin current, before the CONTROL pin
voltage has had a chance to discharge to the lower threshold
voltage of approximately 4.8 V (internal supply under-voltage
lockout threshold). When the externally fed current charges the
CONTROL pin to the shunt regulator voltage of 5.8 V, current
Rev. C 06/15
5
TOP232-234
www.power.com
PI-2545-082299
S1 S2 S6 S7 S1 S2 S6 S7S0 S1 S7
S0 S0
5.8 V
4.8 V
S7
0 V
0 V
0 V
V
LINE
V
C
V
DRAIN
V
OUT
Note: S0 through S7 are the output states of the auto-restart counter
2
1234
0 V
~
~
~
~
~
~~
~~
~
S6 S7
~
~~
~
~
~
~
~
V
UV
~
~
~
~
~
~
~
~
S2
~
~
in excess of the consumption of the chip is shunted to
SOURCE through resistor RE as shown in Figure 2. This
current flowing through RE controls the duty cycle of the power
MOSFET to provide closed loop regulation. The shunt
regulator has a finite low output impedance ZC that sets the
gain of the error amplifier when used in a primary feedback
configuration. The dynamic impedance ZC of the CONTROL
pin together with the external CONTROL pin capacitance sets
the dominant pole for the control loop.
When a fault condition such as an open loop or shorted output
prevents the flow of an external current into the CONTROL pin,
the capacitor on the CONTROL pin discharges towards 4.8 V.
At 4.8 V auto-restart is activated which turns the output MOSFET
off and puts the control circuitry in a low current standby
mode. The high-voltage current source turns on and charges
the external capacitance again. A hysteretic internal supply
under-voltage comparator keeps VC within a window of
typically 4.8 to 5.8 V by turning the high-voltage current source
on and off as shown in Figure 5. The auto-restart circuit has a
divide-by-8 counter which prevents the output MOSFET from
turning on again until eight discharge/charge cycles have
elapsed. This is accomplished by enabling the output MOSFET
only when the divide-by-8 counter reaches full count (S7). The
counter effectively limits TOPSwitch-FX power dissipation by
reducing the auto-restart duty cycle to typically 4%. Auto-
restart mode continues until output voltage regulation is again
achieved through closure of the feedback loop.
Oscillator and Switching Frequency
The internal oscillator linearly charges and discharges an
internal capacitance between two voltage levels to create a
sawtooth waveform for the pulse width modulator. The
oscillator sets the pulse width modulator/current limit latch at
the beginning of each cycle.
The nominal switching frequency of 132 kHz was chosen to
minimize transformer size while keeping the fundamental EMI
frequency below 150 kHz. The FREQUENCY pin (available
only in TO-220 package), when shorted to the CONTROL pin,
lowers the switching frequency to 66 kHz (half frequency)
which may be preferable in some cases such as noise
sensitive video applications or a high efficiency standby mode.
Otherwise, the FREQUENCY pin should be connected to the
SOURCE pin for the default 132 kHz. Trimming of the current
reference improves oscillator frequency accuracy.
To further reduce the EMI level, the switching frequency is
jittered (frequency modulated) by approximately ±4 kHz at
250 Hz (typical) rate as shown in Figure 6. Figure 28 shows
the typical improvement of EMI measurements with frequency
jitter.
Pulse Width Modulator and Maximum Duty Cycle
The pulse width modulator implements voltage mode control
by driving the output MOSFET with a duty cycle inversely
proportional to the current into the CONTROL pin that is in
excess of the internal supply current of the chip (see Figure 4).
The excess current is the feedback error signal that appears
across RE (see Figure 2). This signal is filtered by an RC
network with a typical corner frequency of 7 kHz to reduce the
effect of switching noise in the chip supply current generated
Figure 5. Typical Waveforms for (1) Power Up (2) Normal Operation (3) Auto-restart (4) Power Down .
Rev. C 06/15
6
TOP232-234
www.power.com
Figure 6. Switching Frequency Jitter.
by the MOSFET gate driver. The filtered error signal is
compared with the internal oscillator sawtooth waveform to
generate the duty cycle waveform. As the control current
increases, the duty cycle decreases. A clock signal from the
oscillator sets a latch which turns on the output MOSFET. The
pulse width modulator resets the latch, turning off the output
MOSFET. Note that a minimum current must be driven into
the CONTROL pin before the duty cycle begins to change.
The maximum duty cycle, DCMAX, is set at a default maximum
value of 78% (typical). However, by connecting the MULTI-
FUNCTION pin to the rectified DC high-voltage bus through a
resistor with appropriate value, the maximum duty cycle can
be made to decrease from 78% to 38% (typical) as shown in
Figure 8 when input line voltage increases (see line feed-
forward with DCMAX reduction).
Minimum Duty Cycle and Cycle Skipping
To maintain power supply output regulation, the pulse width
modulator reduces duty cycle as the load at the power supply
output decreases. This reduction in duty cycle is proportional
to the current flowing into the CONTROL pin. As the CONTROL
pin current increases, the duty cycle reduces linearly towards
a minimum value specified as minimum duty cycle, DCMIN.
After reaching DCMIN, if CONTROL pin current is increased
further by approximately 0.4 mA, the pulse width modulator
will force the duty cycle from DCMIN to zero in a discrete step
(refer to Figure 4). This feature allows a power supply to
operate in a cycle skipping mode when the load at its output
consumes less power than the power that TOPSwitch-FX
delivers at minimum duty cycle, DCMIN. No additional control is
needed for the transition between normal operation and cycle
skipping. As the load increases or decreases, the power
supply automatically switches between normal operation and
cycle skipping mode as necessary.
Cycle skipping may be avoided, if so desired, by connecting a
minimum load at the power supply output such that the duty
cycle remains at a level higher than DCMIN at all times.
Error Amplifier
The shunt regulator can also perform the function of an error
amplifier in primary feedback applications. The shunt regulator
voltage is accurately derived from a temperature-compensated
bandgap reference. The gain of the error amplifier is set by the
CONTROL pin dynamic impedance. The CONTROL pin
clamps external circuit signals to the VC voltage level. The
CONTROL pin current in excess of the supply current is
separated by the shunt regulator and flows through RE as a
voltage error signal.
On-Chip Current Limit with External Programmability
The cycle-by-cycle peak drain current limit circuit uses the
output MOSFET ON-resistance as a sense resistor. A current
limit comparator compares the output MOSFET on-state drain
to source voltage, VDS(ON) with a threshold voltage. High drain
current causes VDS(ON) to exceed the threshold voltage and
turns the output MOSFET off until the start of the next clock
cycle. The default current limit of TOPSwitch-FX is preset
internally. However, with a resistor connected between
MULTI-FUNCTION pin and SOURCE pin, current limit can be
programmed externally to a lower level between 40% and
100% of the default current limit. Please refer to the graphs in
the typical performance characteristics section for the
selection of the resistor value. By setting current limit low, a
TOPSwitch-FX that is bigger than necessary for the power
required can be used to take advantage of the lower RDS(ON) for
higher efficiency. With a second resistor connected between
the MULTI-FUNCTION pin and the rectified DC high-voltage
bus providing a small amount of feed-forward current, a true
power limiting operation against line variation can be
implemented. When using an RCD clamp, this feed-forward
technique reduces maximum clamp voltage at high line
allowing for higher reflected voltage designs. The current limit
comparator threshold voltage is temperature compensated to
minimize the variation of the current limit due to temperature
related changes in RDS(ON) of the output MOSFET.
The leading edge blanking circuit inhibits the current limit
comparator for a short time after the output MOSFET is turned
on. The leading edge blanking time has been set so that, if a
power supply is designed properly, current spikes caused by
primary-side capacitances and secondary-side rectifier
reverse recovery time will not cause premature termination of
the switching pulse.
The current limit can be lower for a short period after the
leading edge blanking time as shown in Figure 33. This is due
to dynamic characteristics of the MOSFET. To avoid triggering
the current limit in normal operation, the drain current
waveform should stay within the envelope shown.
Line Undervoltage Detection (UV)
At power up, UV keeps TOPSwitch-FX off until the input line
voltage reaches the undervoltage threshold. At power down,
UV prevents auto-restart attempts after the output goes out of
regulation. This eliminates power down glitches caused by
the slow discharge of input storage capacitor present in
applications such as standby supplies. A single resistor
connected from the MULTI-FUNCTION pin to the rectified DC
high-voltage bus sets UV threshold during power up. Once the
power supply is successfully turned on, UV is disabled to
PI-2550-092499
128 kHz
4 ms
Time
Switching
Frequency
VDRAIN
136 kHz
Rev. C 06/15
7
TOP232-234
www.power.com
Figure 7. Synchronization Timing Diagram.
allow extended input voltage operating range. Input voltage is
not checked again until the power supply loses regulation and
attempts another turn-on. This is accomplished by enabling
the UV comparator only when the divide-by-8 counter used in
auto-restart reaches full count (S7) which is also the state that
the counter is reset to at power up (see Figure 5). The UV
feature can be disabled independent of OV feature as shown
in Figure 16.
Line Overvoltage Shutdown (OV)
The same resistor used for UV also sets an overvoltage
threshold which, once exceeded, will force TOPSwitch-FX
output into off-state. The ratio of OV and UV thresholds is
preset at 4.5 as can be seen in Figure 8. This feature turns off
the TOPSwitch-FX power MOSFET when the rectified DC
high-voltage exceeds the OV threshold. When the MOSFET is
off, the rectified DC high-voltage surge capability is increased
to the voltage rating of the MOSFET (700 V), due to the
absence of the reflected voltage and leakage spikes on the
drain. Small amount of hysteresis is provided on the OV
threshold to prevent noise triggering. The OV feature can be
disabled independent of UV feature as shown in Figure 15.
Line Feed-Forward with DCMAX Reduction
The same resistor used for UV and OV also implements line
voltage feed-forward which minimizes output line ripple and
reduces power supply output sensitivity to line transients. This
feed-forward operation is illustrated in Figure 4 by the different
values of IM. Note that for the same CONTROL pin current,
higher line voltage results in smaller operating duty cycle. As
an added safety measure, the maximum duty cycle DCMAX is
also reduced from 78% (typical) at a voltage slightly higher
than the UV threshold to 38% (typical) at the OV threshold (see
Figures 4, 8). DCMAX of 38% at the OV threshold was chosen
to ensure that the power capability of the TOPSwitch-FX is not
restricted by this feature under normal operation.
Remote ON/OFF and Synchronization
TOPSwitch-FX can be turned on or off by controlling the
current into or out from the MULTI-FUNCTION pin (see Figure
8). This allows easy implementation of remote ON/OFF control
of TOPSwitch-FX in several different ways. A transistor or an
optocoupler output connected between the MULTI-FUNCTION
pin and the SOURCE pin implements this function with
“active-on” (Figure 19) while a transistor or an optocoupler
output connected between the MULTI-FUNCTION pin and the
CONTROL pin implements the function with “active-off”
(Figure 20).
When a signal is received at the MULTI-FUNCTION pin to
disable the output through any of the MULTI-FUNCTION pin
functions such as OV, UV and remote ON/OFF, TOPSwitch-FX
always completes its current switching cycle as illustrated in
Figure 7 before the output is forced off. The internal oscillator
is stopped slightly before the end of the current cycle and
stays there as long as the disable signal exists. When the
signal at the MULTI-FUNCTION pin changes state from disable
to enable, the internal oscillator starts the next switching cycle.
This approach allows the use of this pin to synchronize
TOPSwitch-FX to any external signal with a frequency lower
than its internal switching frequency.
As seen above, the remote ON/OFF feature allows the
TOPSwitch-FX to be turned on and off instantly, on a cycle-by-
cycle basis, with very little delay. However, remote ON/OFF
can also be used as a standby or power switch to turn off the
TOPSwitch-FX and keep it in a very low power consumption
state for indefinitely long periods. If the TOPSwitch-FX is held
in remote off state for long enough time to allow the CONTROL
pin to dishcharge to the internal supply undervoltage threshold
of 4.8 V (approximately 32 ms for a 47 µF CONTROL pin
capacitance), the CONTROL pin goes into the hysteretic mode
of regulation. In this mode, the CONTROL pin goes through
Time
Rev. C 06/15
8
TOP232-234
www.power.com
alternate charge and discharge cycles between 4.8 V and
5.8 V (see CONTROL pin operation section above) and runs
entirely off the high-voltage DC input, but with very low power
consumption (160 mW typical at 230 VAC with M pin open).
When the TOPSwitch-FX is remotely turned on after entering
this mode, it will initiate a normal start-up sequence with
soft-start the next time the CONTROL pin reaches 5.8 V. In the
worst case, the delay from remote on to start-up can be equal
to the full discharge/charge cycle time of the CONTROL pin,
which is approximately 125 ms for a 47 µF CONTROL pin
capacitor. This reduced consumption remote off mode can
eliminate expensive and unreliable in-line mechanical switches.
It also allows for microprocessor controlled turn-on and
turn-off sequences that may be required in certain applications
such as inkjet and laser printers. See Figure 27 under
application examples for more information.
Soft-Start
An on-chip soft-start function is activated at start-up with a
duration of 10 ms (typical). Maximum duty cycle starts from
zero and linearly increases to the default maximum of 78% at
the end of the 10 ms duration. In addition to start-up, soft-
start is also activated at each restart attempt during auto-
restart and when restarting after being in hysteretic regulation
of CONTROL pin voltage (VC), due to remote off or thermal
shutdown conditions. This effectively minimizes current and
voltage stresses on the output MOSFET, the clamp circuit and
the output rectifier, during start-up. This feature also helps
minimize output overshoot and prevents saturation of the
transformer during start-up.
Shutdown/Auto-Restart
To minimize TOPSwitch-FX power dissipation under fault
conditions, the shutdown/auto-restart circuit turns the power
supply on and off at an auto-restart duty cycle of typically 4%
if an out of regulation condition persists. Loss of regulation
interrupts the external current into the CONTROL pin. VC
regulation changes from shunt mode to the hysteretic auto-
restart mode described above. When the fault condition is
removed, the power supply output becomes regulated, VC
regulation returns to shunt mode, and normal operation of the
power supply resumes.
Hysteretic Over-Temperature Protection
Temperature protection is provided by a precision analog
circuit that turns the output MOSFET off when the junction
temperature exceeds the thermal shutdown temperature
(135 ˚C typical). When the junction temperature cools to below
the hysteretic temperature, normal operation resumes. A large
hysteresis of 70 ˚C (typical) is provided to prevent overheating
of the PC board due to a repeating fault condition. VC is
regulated in hysteretic mode and a 4.8 V to 5.8 V (typical)
sawtooth waveform is present on the CONTROL pin when the
power supply is turned off.
Bandgap Reference
All critical TOPSwitch-FX internal voltages are derived from a
temperature-compensated bandgap reference. This reference
is also used to generate a temperature-compensated current
reference which is trimmed to accurately set the switching
frequency, MOSFET gate drive current, current limit, and the
line OV/UV thresholds. TOPSwitch-FX has improved circuitry
to maintain all of the above critical parameters within very tight
absolute and temperature tolerances.
High-Voltage Bias Current Source
This current source biases TOPSwitch-FX from the DRAIN pin
and charges the CONTROL pin external capacitance during
start-up or hysteretic operation. Hysteretic operation occurs
during auto-restart, remote off and over-temperature shutdown.
In this mode of operation, the current source is switched on
and off with an effective duty cycle of approximately 35%.
This duty cycle is determined by the ratio of CONTROL pin
charge (IC) and discharge currents (ICD1 and ICD2). This current
source is turned off during normal operation when the output
MOSFET is switching.
Rev. C 06/15
9
TOP232-234
www.power.com
4
4 4 4
4 4 4
4 4
4
4 4 4 4
4 4 4 4 4
Table 2. Typical MULTI-FUNCTION Pin Configurations.
MULTI-FUNCTION PIN TABLE*
13 14 15 16 17 18 19 20 21 22 23
*This table is only a partial list of many MULTI-FUNCTION pin configurations that are possible.
Using FREQUENCY and MULTI-FUNCTIONAL Pins
FREQUENCY (F) Pin Operation
The FREQUENCY pin is a digital input pin available in TO-220
package only. Shorting the FREQUENCY pin to SOURCE pin
selects the nominal switching frequency of 132 kHz (Figure 10)
which is suited for most applications. For other cases that
may benefit from lower switching frequency such as noise
sensitive video applications, a 66 kHz switching frequency (half
frequency) can be selected by shorting the FREQUENCY pin
to the CONTROL pin (Figure 11). In addition, an example
circuit shown in Figure 12 may be used to lower the switching
frequency from 132 kHz in normal operation to 66 kHz in
standby mode for very low standby power consumption.
MULTI-FUNCTION (M) Pin Operation
When current is fed into the MULTI-FUNCTION pin, it works as
a voltage source of approximately 2.6 V up to a maximum
current of +400 µA (typical). At +400 µA, this pin turns into a
constant current sink. When current is drawn out of the
MULTI-FUNCTION pin, it works as a voltage source of
approximately 1.32 V up to a maximum current of –240 µA
(typical). At –240 µA, it turns into a constant current source.
Refer to Figure 9.
There are a total of five functions available through the use of
the MULTI-FUNCTION pin: OV, UV, line feed-forward with
DCMAX reduction, external current limit and remote ON/OFF. A
short circuit between the MULTI-FUNCTION pin and SOURCE
pin disables all five functions and forces TOPSwitch-FX to
operate in a simple three terminal mode like TOPSwitch-II. The
MULTI-FUNCTION pin is typically used for line sensing by
s
Figure Number
Three Terminal Operation
Undervoltage
Overvoltage
Line Feed-forward (DCMAX)
Line Feed-forward (ILIMIT)
External Current Limit
Remote ON/OFF
connecting a resistor from this pin to the rectified DC high-
voltage bus to implement OV, UV and DCMAX reduction with
line voltage functions. In this mode, the value of the resistor
determines the line OV/UV thresholds, and the DCMAX is
reduced linearly with rectified DC high-voltage starting from
just above the UV threshold. In high efficiency applications
this pin can be used in the external current limit mode instead,
to reduce the current limit externally to a value close to the
operating peak current, by connecting the pin to the SOURCE
pin through a resistor. The same pin can also be used as a
remote on/off and a synchronization input in both modes.
Please refer to Table 2 for possible combinations of the
functions with example circuits shown in Figure 13 through
Figure 23. A description of specific functions in terms of the
MULTI-FUNCTION pin I/V characteristic is shown in Figure 8.
The horizontal axis represents MULTI-FUNCTION pin current
with positive polarity indicating currents flowing into the pin.
The meaning of the vertical axes varies with functions. For
those that control the on/off states of the output such as UV,
OV and remote ON/OFF, the vertical axis represents the enable/
disable states of the output. UV triggers at IUV (+50 µA typical)
and OV triggers at IOV (+225 µA typical). Between +50 µA and
+225 µA, the output is enabled. For external current limit and
line feed-forward with DCMAX reduction, the vertical axis
represents the magnitude of the ILIMIT and DCMAX. Line feed-
forward with DCMAX reduction lowers maximum duty cycle
from 78% at IM(DC) (+90 µA typical) to 38% at IOV (+225 µA).
External current limit is available only with negative MULTI-
FUNCTION pin current. Please see graphs in the typical
performance characteristics section for the current limit program-
ming range and the selection of appropriate resistor value.
Rev. C 06/15
10
TOP232-234
www.power.com
-250 -200 -150 -100 -50 050 100 150 200 250 300 350 400
PI-2524-081999
Output
MOSFET
Switching
(Enabled)
(Disabled)
I
LIMIT
(Default)
DC
MAX
(78.5%)
Current
Limit
Maximum
Duty Cycle
V
BG
V
BG
+ V
TP
I
M
I
M
I
M
I
M
I
UV
I
REM(N)
I
OV
MULTI-
FUNCTION
Pin Voltage
Note: This figure provides idealized functional characteristics of the MULTI-FUNCTION pin with typical performance values.
Please refer to the parametric table and typical performance characteristics sections of the data sheet for measured data.
MULTI-FUNCTION Pin Current (µA)
Disabled when supply
output goes out of
regulation
Figure 8. MULTI-FUNCTION Pin Characteristics.
Figure 9. MULTI-FUNCTION Pin Input Simplified Schematic.
V
BG
+ V
T
V
BG
240 µA
400 µA
CONTROL Pin
MULTI-FUNCTION Pin
(Positive Current Sense - Undervoltage,
Overvoltage, Maximum Duty
Cycle Reduction)
(Negative Current Sense - ON/OFF,
Current Limit Adjustment)
PI-2548-062515
TOPSwitch-FX
Rev. C 06/15
11
TOP232-234
www.power.com
Figure 12. Half Frequency Standby Mode (For High Standby Efficiency).
Figure 10. Full Frequency Operation (132 kHz). Figure 11. Half Frequency Operation (66 kHz).
Typical Uses of FREQUENCY (F) Pin
PI-2506-081199
DC
Input
Voltage
+
-
D
S
C
CONTROL
F
Rev. C 06/15
12
TOP232-234
www.power.com
Figure 15. Line Sensing for Undervoltage Only (Overvoltage Disabled).
PI-2510-040401
DC
Input
Voltage
+
-
DM
S
C
V
UV
= R
LS
x I
UV
For Value Shown
V
UV
= 100 VDC
R
LS
6.2 V
2 MΩ
22 kΩ
CONTROL
Figure 16. Line Sensing for Overvoltage Only (Undervoltage Disabled).
Figure 17. Externally Set Current Limit.
PI-2517-040401
DC
Input
Voltage
+
-
DM
S
C
For R
IL
= 12 kΩ
I
LIMIT
= 67%
CONTROL
R
IL
See graph for other
resistor values (R
IL
)
For R
IL
= 25 kΩ
I
LIMIT
= 40%
Figure 13. Three Terminal Operation (MULTI-FUNCTION Features Disabled.
FREQUENCY Pin Tied to SOURCE or CONTROL Pin).
Figure 14. Line Sensing for Undervoltage, Overvoltage and Maximum Duty
Cycle Reduction.
PI-2508-081199
DC
Input
Voltage
+
-
D
S
C
CONTROL
M
Typical Uses of MULTI-FUNCTION (M) Pin
Figure 18. Current Limit Reduction with Line Voltage.
Rev. C 06/15
13
TOP232-234
www.power.com
Figure 20. Active-Off Remote ON/OFF.
Figure 19. Active-on (Fail Safe) Remote ON/OFF.
PI-2523-062915
DC
Input
Voltage
+
-
D
S
C
R
LS
M
For R
LS
= 2
MΩ
V
UV
= 100 VDC
V
OV
= 450 VDC
CONTROL
Q
R
2 MΩ
Q
R
can be an optocoupler
output or can be replaced
by a manual switch.
ON/OFF
47 kΩ
Figure 23. Active-off Remote ON/OFF with Line Sense.
Figure 22. Active-off Remote ON/OFF with Externally Set Current Limit.
PI-2521-040401
DC
Input
Voltage
+
-
D
S
C
R
IL
R
MC
24 kΩ
12 kΩ
M
CONTROL
Q
R
2RIL
RMC =
QR can be an optocoupler
output or can be replaced
by a manual switch.
ON/OFF
47 kΩ
Figure 21. Active-on Remote ON/OFF with Externally Set Current Limit.
Typical Uses of MULTI-FUNCTION (M) Pin (cont.)
Rev. C 06/15
14
TOP232-234
www.power.com
Figure 24. 30 W Power Supply using External Current Limit.
Application Examples
A High Efficiency, 30 W, Universal Input Power Supply
The circuit shown in Figure 24 takes advantage of several of
the TOPSwitch-FX features to reduce system cost and power
supply size and to improve efficiency. This design delivers 30 W
at 12 V, from an 85 to 265 VAC input, at an ambient of 50 ˚C,
in an open frame configuration. A nominal efficiency of 80% at
full load is achieved using TOP234.
The current limit is externally set by resistors R1 and R2 to a
value just above the low line operating peak current of
approximately 70% of the default current limit. This allows use
of a smaller transformer core size and/or higher transformer
primary inductance for a given output power, reducing
TOPSwitch-FX power dissipation, while at the same time
avoiding transformer core saturation during startup and output
transient conditions. The resistor R1 provides a feed-forward
signal that reduces the current limit with increasing line
voltage, which, in turn, limits the maximum overload power at
high input line voltage. The feed-forward function in
combination with the built-in soft-start feature of TOPSwitch-
FX, allows the use of a low cost RCD clamp (R3, C3 and D1)
with a higher reflected voltage, by safely limiting the
TOPSwitch-FX drain voltage, with adequate margin, under
worst case conditions. The extended maximum duty cycle
feature of TOPSwitch-FX (guaranteed minimum value of 75%
vs. 64% for TOPSwitch-II) allows the use of a smaller input
capacitor (C1). The extended maximum duty cycle and the
higher reflected voltage possible with the RCD clamp also
permit the use of a higher primary to secondary turns ratio for
T1 which reduces the peak reverse voltage experienced by the
secondary rectifier D8. As a result, a 60 V Schottky rectifier
can be used for up to 15 V outputs, which greatly improves
power supply efficiency. The cycle skipping feature of the
TOPSwitch-FX eliminates the need for any dummy loading for
regulation at no load and reduces the no load/standby
consumption of the power supply. Frequency jitter provides
improved margin for conducted EMI meeting the CISPR 22
(FCC B) specification.
A simple Zener sense circuit is used for low cost. The output
voltage is determined by the Zener diode (VR2) voltage and
the voltage drops across the optocoupler (U2) LED and
resistor R6. Resistor R8 provides bias current to Zener VR2 for
typical regulation of ±5% at the 12 V output level, over line and
load and component variations.
12 V
@ 2.5 A
D2
1N4148
T1
C5
47 µF
10 V
U2
LTV817A
VR2
1N5240C
10 V, 2%
R6
150 Ω
R15
150 Ω
C14
1 nF
D1
UF4005
R3
68 kΩ
2W
C3
4.7 nF
1KV
CY1
2.2 nF
U1
TOP234Y
D M
S F
C
TOPSwitch-FX
R8
150 Ω
C1
68 µF
400 V
C6
100 nF
D8
MBR1060 C10
560 µF
35 V
C12
220 µF
35 V
C11
560 µF
35 V
CONTROL
CONTROL
RTN
R5
6.8 Ω
R1
4.7 MΩ
1/2 W
R2
9.09 kΩ
PI-2525-062515
L3
3.3 µH
BR1
600 V
2A
F1
3.15 A
J1
L1
20 mH
L
N
CX1
100 nF
250 VAC
Rev. C 06/15
15
TOP232-234
www.power.com
Figure 25. 35 W Set-Top Box Power Supply.
35 W Multiple Output Power Supply
Figure 25 shows a five output, 35 W, secondary regulated
power supply utilizing a TOP233 for multiple output applications
such as set-top box, VCR, DVD, etc. The circuit shown is
designed for a 230 VAC input but can be used over the
universal range at a derated output power of 25 W. Alternatively,
a doubler input stage can be used at 100 or 115 VAC for the
full power rating of 35 W. TOPSwitch-FX provides several
advantages in the above mentioned applications.
A single line sense resistor R1 (2 MΩ) implements an under-
voltage detect (at 100 V), overvoltage shutdown (at 450 V) and
line feed-forward with DCMAX reduction features. Under-
voltage detect ensures that the outputs are glitch free on
power down. The over-voltage shutdown turns off the
TOPSwitch-FX MOSFET above 450 V on the DC input rail,
eliminating reflected voltage and leakage inductance spikes,
and hence, extending the surge withstand to the 700 VDC
rating of the MOSFET. This feature prevents field failures in
countries where prolonged line voltage surges are common.
This design also takes advantage of soft-start and higher
operating frequency to reduce transformer size. A snubber
circuit (R4, C4) is used to slowdown dv/dt of the switching
waveform minimizing radiated video noise that could interfere
with TV reception. The half frequency option of the TOPSwitch-FX
can be used by connecting the FREQUENCY pin to the
CONTROL pin instead of the SOURCE pin in video noise
sensitive applications to allow for heavier snubbing without
significant impact on efficiency.
This design achieves ±5% load regulation on 3.3 V and 5 V
outputs using dual sensed optocoupler feedback through
resistors R9, R10 and R11. Other output voltages are set by
the transformer turns ratio. Output voltage on the low power
-5 V output is shunt regulated by resistor R12 and Zener diode
VR2. Dummy load resistor R13 is required to maintain
regulation of the 30 V output under light load conditions.
Compensation of the TL431 (U3) is achieved with resistor R8
and capacitor C7. Primary side compensation and auto-
restart frequency are determined by resistor R5 and capacitor
C5. Second stage LC post-filtering is used on the 3.3 V, 5 V
and 18 V high power outputs (L2, L3, L4 and C13, C15, C17)
for low ripple. Full load operating efficiency exceeds 75%
across the AC input range. Primary clamp components VR1
and D1 limit peak drain voltage to a safe value.
The frequency jittering in TOPSwitch-FX helps reduce EMI,
maintaining emissions below CISPR 22 (FCC B) levels through
proper choice of Y1 capacitor (CY1) and input filtering elements
(CX1, L1). To minimize coupling of common mode transients to
the TOP233, Y1 capacitor is tied to the positive input DC rail.
Lightning strike immunity to 3 kV is attained with the addition
of a 275 V MOV (RV1).
5 V
@ 2.5 A
3.3 V
@ 3 A
RTN
D2
1N4148
T1
U2
LTV817
U3
TL431CLP
C8
22 µF
R6
51 Ω
R11
10.0 kΩ
C7
0.1 µF
R9
9.53 kΩ
R10
15.0 kΩ
R8
10 Ω
R7
510 Ω
D8
MUR120
D9
UF5402
C12
220 µF
25 V
CY1
2.2 nF
30 V
@ 100 mA
18 V
@ 550 mA
D1
UF4007
VR1
P6KE200
BR1
400 V
F1
3.15 A
RV1
275 V
J1
L1
20 mH
L
N
R5
6.8 Ω
C5
47 µF
C4
47 pF
U1
TOP233Y
D M
S F
C
TOPSwitch-FX
R1
2 MΩ
1/2 W
R13
24 kΩ
R4
2 kΩ
C1
33 µF
400 V
C6
100 nF
C10
100 µF
50 V
D10
MBR1045
C14
1000 µF
25 V
L3
3.3 µH
L4
3.3 µH
C15
100 µF
10 V
C13
100 µF
25 V
C11
1 µF
50 V
L2
3.3 µH
D11
BYW29-
100
C16
1000 µF
25 V
C18
330 µF
10 V R12
5 Ω
D12
1N5819 -5 V
@ 100 mA
CX1
0.1 µF
250 VAC
C17
100 µF
10 V
C19
100 µF
10 V
VR2
1N5231
PI-2536-062515
CONTROL
CONTROL
Rev. C 06/15
16
TOP232-234
www.power.com
17 W PC Standby Power Supply
Figure 26 shows a 17 W PC standby application with 3.3 V
and 5 V secondary outputs and a 15 V primary output. The
supply uses the TOP232 operating from 230 VAC or 100/
115 VAC with doubler input. This design takes advantage of
the soft-start, line under-voltage detect, tighter current limit
variation and higher switching frequency features of
TOPSwitch-FX. For example, the higher switching frequency
with tighter current limit variation allows use of an EE19
transformer core. Furthermore, the spacing between high-
voltage DRAIN pin and low voltage pins of the TOPSwitch-FX
packages provides large creepage distance which is a
significant advantage in high pollution environments such as
fan cooled PC power supplies.
Capacitor C1 provides high frequency decoupling of the
high-voltage DC supply, and is necessary only if there is a long
trace length from the source of the DC supply to the inputs of
this standby circuit. The line sense resistor R1 senses the DC
input voltage for line undervoltage. When AC is turned off, the
under-voltage detect feature of the TOPSwitch-FX prevents
auto-restart glitches at the output caused by the slow
discharge of large storage capacitance in the main converter.
This is achieved by turning the power supply off when the
input voltage goes below a level needed to maintain output
regulation and keeping it off until the input voltage goes above
the under-voltage threshold (VUV), when the AC is turned on
again. The under voltage threshold is set at 200VDC, slightly
below the required lowest operating DC input voltage, for
start-up at 170VAC. This feature saves several components
needed to implement the glitch free turn off with discrete or
TOPSwitch-II based designs.
The bias winding is rectified and filtered by D2 and C6 to
create a bias voltage for the TOP232 and to provide a 15V
primary bias output voltage for the main power supply primary
control circuitry. Both 3.3V and 5V output voltages are
sensed by R9, R10 and R11 using a TL431 (U3) circuit shown.
Resistor R6 limits current through optocoupler U2 and sets
overall AC control loop gain. Resistor R7 assures that there is
sufficient bias current for the TL431 when the optocoupler is at
a minimum current. Capacitor C8 provides a soft-finish
function to eliminate turn-on overshoot. The no load regulation
(cycle-skipping) of TOPSwitch-FX permits the circuit to meet
the low standby power requirement of the Blue Angel
specification for PCs.
Figure 26. 17 W PC Standby Supply.
3.3 V
@ 2 A
200 - 375
VDC
D2
BAV21
T1
C8
10 µF
35 V
C11
100 µF
10 V
C5
47 µF
U2
SFH615-2
U3
TL431CLP
C7
0.1 µF
R6
301 ΩR9
16.2 kΩ
D1
UF4005
VR1
BZY97C-
200
U1
TOP232Y
D M
S F
C
TOPSwitch-FX
R7
510 Ω
C1
0.01 µF
1 kV
(optional)
(Primary
Referenced)
C6
35 V
D4
SB540
D3
SB540
5 V
@ 2 A
C12
1000 µF
10 V
C10
1000 µF
10 V
CY1
1 nF
+
–
PI-2537-062515
RTN
15 V
@ 30 mA
R5
6.8 Ω
R1
3.9 MΩ
L2
3.3 µH
L1
3.3 µH
R10
12.1 kΩ
R11
10 kΩ
C13
100 µF
10 V
CONTROL
CONTROL
Rev. C 06/15
17
TOP232-234
www.power.com
Processor Controlled Supply Turn On/Off
A low cost momentary contact switch can be used to turn the
TOPSwitch-FX power on and off under microprocessor control
that may be required in some applications such as printers.
The low power remote off feature allows an elegant implemen-
tation of this function with very few external components as
shown in Figure 27. Whenever the push button momentary
contact switch P1 is closed by the user, the optocoupler U3 is
activated to inform the microprocessor of this action. Initially,
when the power supply is off (M pin is floating), closing of P1
turns the power supply on by shorting the M pin of the
TOPSwitch-FX to SOURCE through a diode (remote on). When
the secondary output voltage VCC is established, the micro-
processor comes alive and recognizes that the switch P1 is
closed through the switch status input that is driven by the
optocoupler U3 output. The microprocessor then sends a
power supply control signal to hold the power supply in the
on-state through the optocoupler U4. If the user presses the
switch P1 again to command a turn off, the microprocessor
detects this through the optocoupler U3 and initiates a
shutdown procedure that is product specific. For example, in
the case of the inkjet printer, the shutdown procedure may
include safely parking the print heads in the storage position.
In the case of products with a disk drive, the shutdown
procedure may include saving data or settings to the disk.
After the shutdown procedure is complete, when it is safe to
turn off the power supply, the microprocessor releases the
M pin by turning the optocoupler U4 off. If the manual switch
and the optocouplers U3 and U4 are not located close to the
M pin, a capacitor CM may be needed to prevent noise
coupling to the pin when it is open.
The power supply could also be turned on remotely through a
local area network or a parallel or serial port by driving the
optocoupler U4 input LED with a logic signal. Sometimes it is
easier to send a train of logic pulses through a cable (due to
AC coupling of cable, for example) instead of a DC logic level
as a wake-up signal. In this case, a simple RC filter can be
used to generate a DC level to drive U4 (not shown in Figure
27). This remote on feature can be used to wake-up
peripherals such as printers, scanners, external modems, disk
drives, etc., as needed from a computer. Peripherals are
usually designed to turn off automatically if they are not being
used for a period of time, to save power.
Figure 27. Remote ON/OFF using Microcontroller.
U1
U2
U4 U3
C
M
P1
PI-2561-062615
V
CC
(+5 V)
RETURN
CONTROL
High-Voltage
DC Input
TOPSwitch-FX
D M
S F
C
1N4148
U4
LTV817A
6.8 kΩ
1 nF
100 kΩ
6.8 kΩ
U3
LTV817A
27 kΩ
1N4148
47 µFP1 Switch
Status
Power
Supply
ON/OFF
Control
External
Wake-up
Signal
LOGIC
INPUT
LOGIC
OUTPUT
MICRO-
PROCESSOR/
CONTROLLER
+
–
Rev. C 06/15
18
TOP232-234
www.power.com
In addition to using a minimum number of components,
TOPSwitch-FX provides many technical advantages in this
type of application:
1. Extremely low power consumption in the off mode: 80 mW
typical at 110 VAC and 160 mW typical at 230 VAC. This is
because in the remote/off mode the TOPSwitch-FX
consumes very little power, and the external circuitry does
not consume any current (M pin is open) from the high-
voltage DC input.
2. A very low cost, low voltage/current, momentary contact
switch can be used.
3. No debouncing circuitry for the momentary switch is
required. During turn-on, the start-up time of the power
supply (typically 10 to 20 ms) plus the microprocessor
initiation time act as a debouncing filter, allowing a turn-on
only if the switch is depressed firmly for at least the above
delay time. During turn-off, the microprocessor initiates the
shutdown sequence when it detects the first closure of the
switch, and subsequent bouncing of the switch has no
effect. If necessary, the microprocessor could implement
the switch debouncing in software during turn-off, or a filter
capacitor can be used at the switch status input.
4. No external current limiting circuitry is needed for the
operation of the U4 optocoupler output due to internal
limiting of M pin current.
5. No high-voltage resistors to the input DC voltage rail are
required to power the external circuitry in the primary. Even
the LED current for U3 can be derived from the CONTROL
pin. This not only saves components and simplifies layout,
but also eliminates the power loss associated with the
high-voltage resistors in both on and off states.
6. Robust design: There is no on/off latch that can be
accidentally triggered by transients. Instead, the power
supply is held in the on-state through the secondary side
microprocessor.
Rev. C 06/15
19
TOP232-234
www.power.com
Key Application Considerations
TOPSwitch-FX vs. TOPSwitch-ll
Table 3 compares the features and performance differences
between TOPSwitch-FX and TOPSwitch-II. Many of the new
features eliminate the need for costly discrete component.
Other features increase the robustness of design allowing
cost savings in the transformer and other power components.
*Not available
Table 3. Comparison Between TOPSwitch-II and TOPSwitch-FX. (continued on next page)
Function TOPSwitch-II TOPSwitch-FX Figures Advantages
Soft-Start N/A* 10 ms • Limits peak current and voltage
component stresses during start-up
• Eliminates external components
used for soft-start in most applications
• Minimizes output overshoot
External Current Limit N/A* Programmable 8, 17, • Smaller transformer
100% to 40% of 18, 21, • Higher efficiency
default current 22 • Allows tighter power limit
limit during output overload conditions
DCMAX 67% 78% 4 • Smaller input cap (wider dynamic range)
• Higher power capability (when used
with RCD clamp for large VOR)
• Allows use of Schottky secondary
rectifier diode for up to 15 V output
for high efficiency
Line Feed-forward with N/A* 78% to 38% 4, 8, 14, • Rejects line ripple
DCMAX Reduction 23 • Increases transient and surge voltage
withstand capability
Line OV Shutdown N/A* Single resistor 8, 14, • Increases voltage withstand capability
programmable 16, 23 against line surge
Line UV Detection N/A* Single resistor 5, 8, 14, • Prevents auto-restart glitches during
programmable 15, 23 power-down
Switching Frequency 100 kHz ±10% 132 kHz ±7% 10 • Smaller transformer
• Fundamental below 150 kHz for
conducted EMI
Switching Frequency N/A* 66 kHz ±7% 11, 12 • Lower losses when using RC and RCD
Option (TO-220 only) snubber for noise reduction in video
applications
• Allows for higher efficiency in standby
mode
• Lower EMI (second harmonic below
150 kHz)
Frequency Jitter N/A* ±4 kHz@132 kHz 6, 28 • Reduces conducted EMI
±2 kHz@66 kHz
Cycle Skipping N/A* At DCMIN (1.5%) 4 • Zero load regulation without dummy
load
• Low power consumption at no load
Rev. C 06/15
20
TOP232-234
www.power.com
TOPSwitch-FX Design Considerations
TOPSwitch-FX Selection
Selecting the optimum TOPSwitch-FX depends upon required
maximum output power, efficiency, heat sinking constraints
and cost goals. With the option to externally reduce current
limit, a larger TOPSwitch-FX may be used for lower power
applications where higher efficiency is needed or minimal heat
sinking is available.
Input Capacitor
The input capacitor must be chosen to provide the minimum
DC voltage required for the TOPSwitch-FX converter to
maintain regulation at the lowest specified input voltage and
maximum output power. Since TOPSwitch-FX has a higher
DCMAX than TOPSwitch-II, it is possible to use a smaller input
capacitor. For TOPSwitch-FX, a capacitance of 2 µF per watt
is usually sufficient for universal input with an appropriately
designed transformer.
Primary Clamp and Output Reflected Voltage VOR
A primary clamp is necessary to limit the peak TOPSwitch-FX
drain to source voltage. A Zener clamp (see Figure 26, VR1)
requires few parts and takes up little board space. For good
efficiency, the clamp Zener should be selected to be at least
1.5 times the output reflected voltage VOR as this keeps the
leakage spike conduction time short. When using a Zener
clamp in a universal input application, a VOR of less than 135 V
is recommended to allow for the absolute tolerances and
temperature variations of the Zener. This will ensure efficient
operation of the clamp circuit and will also keep the maximum
drain voltage below the rated breakdown voltage of the
TOPSwitch-FX MOSFE T.
A high VOR is required to take full advantage of the wider DCMAX
of TOPSwitch-FX. An RCD clamp provides tighter clamp
voltage tolerance than a Zener clamp and allows a VOR as high
as 165 V. The VOR can be further increased in continuous
mode designs up to 185 V by reducing the external current
limit as a function of input line voltage (see Figure 18). The
RCD clamp is more cost effective than the Zener clamp but
requires more careful design (see quick design checklist).
*Not available
Table 3 (cont). Comparison Between TOPSwitch-II and TOPSwitch-FX.
Function TOPSwitch-II TOPSwitch-FX Figures Advantages
Remote ON/OFF N/A* Single transistor 8, 19, • Fast on/off (cycle by cycle)
or optocoupler 20, 21, • Active-on or active-off control
interface or manual 22, 23, • Low consumption in remote off state
switch 27 • Active-on control for fail-safe
• Eliminates expensive in-line on/off
switch
• Allows processor controlled turn on/off
• Permits shutdown/wake-up of
peripherals via LAN or parallel port
Synchronization N/A* Single transistor • Synchronization to external lower
or optocoupler frequency signal
interface • Starts new switching cycle on demand
Thermal Shutdown Latched Hysteretic (with • Automatic recovery from thermal fault
70 °C hysteresis) • Large hysteresis prevents circuit
board overheating
Current Limit Tolerance ±10% (@25 °C) ±7% (@25 °C) • 10% higher power capability due to
-8% (0 °C to100 °C) -4% (0 °C to 100 °C) tighter tolerance
DRAIN DIP 0.037” / 0.94 mm 0.137” / 3.48 mm • Greater immunity to arcing as a
Creepage at SMD 0.037” / 0.94 mm 0.137” / 3.48 mm result of build-up of dust, debris and
Package TO-220 0.046” / 1.17 mm 0.068” / 1.73 mm other contaminants
DRAIN Creepage at 0.045” / 1.14 mm 0.113” / 2.87 mm • Preformed leads accommodate
PCB for TO-220 (preformed leads) large creepage for PCB layout
• Easier to meet Safety (UL/VDE)
Rev. C 06/15
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TOP232-234
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Output Diode
The output diode is selected for peak inverse voltage, output
current, and thermal conditions in the application (including
heat sinking, air circulation, etc.). The higher DCMAX of
TOPSwitch-FX along with an appropriate transformer turns
ratio can allow the use of a 60 V Schoktty diode for higher
efficiency on output voltages as high as 15 V (See Figure 24.
A 12 V, 30 W design using a 60 V Schottky for the output
diode).
Soft-Start
Generally a power supply experiences maximum stress at
start-up before the feedback loop achieves regulation. For a
period of 10 ms the on-chip soft-start linearly increases the
duty cycle from zero to the default DCMAX at turn on, which
causes the primary current and output voltage to rise in an
orderly manner allowing time for the feedback loop to take
control of the duty cycle. This reduces the stress on the
TOPSwitch-FX MOSFET, clamp circuit and output diode(s),
and helps prevent transformer saturation during start-up. Also,
soft-start limits the amount of output voltage overshoot, and in
many applications eliminates the need for a soft-finish
capacitor.
EMI
The frequency jitter feature modulates the switching frequency
over a narrow band as a means to reduce conducted EMI
peaks associated with the harmonics of the fundamental
switching frequency. This is particularly beneficial for average
detection mode. As can be seen in Figure 28, the benefits of
jitter increase with the order of the switching harmonic due to
an increase in frequency deviation.
The FREQUENCY pin of TOPSwitch-FX offers a switching
frequency option of 132 kHz or 66 kHz. In applications that
require heavy snubbers on the drain node for reducing high
frequency radiated noise (for example, video noise sensitive
applications such as VCR, DVD, monitor, TV, etc.), operating at
66 kHz will reduce snubber loss resulting in better efficiency.
Also, in applications where transformer size is not a concern,
use of the 66 kHz option will provide lower EMI and higher
efficiency. Note that the second harmonic of 66 kHz is still
below 150 kHz, above which the conducted EMI specifications
get much tighter.
For 10 W or below, it is possible to use a simple inductor in
place of a more costly AC input common mode choke to meet
worldwide conducted EMI limits.
Transformer Design
It is recommended that the transformer be designed for
maximum operating flux density of 3000 gauss and a peak
flux density of 4200 gauss at maximum current limit. The
turns ratio should be chosen for a reflected voltage (VOR) no
greater than 135 V when
Switching Harmonic
PI-2559-093099
Noise Reduction (dB)
Quasi-Peak
Average
-20
-10
0
-10
20
30
40
50
60
70
80
0.15 1 10 30
Frequency (MHz)
Amplitude (dBµV)
PI-2576-062615
VFG243B (QP)
VF646B (AV)
TOPSwitch-II (no jitter)
VFG243B (QP)
VF646B (AV)
-20
-10
0
-10
20
30
40
50
60
70
80
0.15 1 10 30
Frequency (MHz)
Amplitude (dBµV)
PI-2577-062615
TOPSwitch-FX (with jitter)
(a)
(b)
(c)
Figure 28. (a) Conducted Noise Improvement for Low Frequency
Harmonics due to Jitter, (b) TOPSwitch-II Full Range EMI Scan
(100 kHz, no Jitter), (c) TOPSwitch-FX Full Range EMI Scan
(132 kHz, with Jitter) with Identical Circuitry and Conditions.
Rev. C 06/15
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TOP232-234
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Figure 29. Layout Considerations for TOPSwitch-FX using DIP or SMD (Using Line Sensing for Under-Voltage and Overvoltage).
TOP VIEW
PI-2543-062615
Y1-
Capacitor
Opto-
coupler
D
+
–
HV J1
R1
+
–DC
Out
Input Filter Capacitor
Output Filter Capacitor
Safety Spacing
T
r
a
n
s
f
o
r
m
e
r
Maximize hatched copper
areas ( ) for optimum
heat sinking
S
PRI SEC
S
S
SC
BIAS
M
TOPSwitch-FX
Figure 30. Layout Considerations for TOPSwitch-FX using TO-220 Package (Using Current Limit Reduction with Line Voltage).
TOP VIEW
PI-2544-062615
Y1-
Capacitor
Opto-
coupler
D
+
–
HV
+– DC
Out
Input Filter Capacitor
Heat Sink
Output Filter Capacitor
Safety Spacing
T
r
a
n
s
f
o
r
m
e
r
Maximize hatched copper
areas ( ) for optimum
heat sinking
PRI SEC
C
J1
R1
R2
TOPSwitch-FX
BIAS
T
r
a
n
s
f
o
r
m
e
r
M
S
F
Rev. C 06/15
23
TOP232-234
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using a Zener clamp, 165 V when using an RCD clamp and
185 V when using RCD clamp with current limit feed-forward.
For designs where operating current is significantly lower than
the default current limit, it is recommended to use an externally
set current limit close to the operating peak current to reduce
peak flux density and peak power (see Figure 17). In most
applications, the tighter current limit tolerance, higher switching
frequency and soft-start features of TOPSwitch-FX contribute
to a smaller transformer when compared to TOPSwitch-II.
Standby Consumption
Cycle skipping can significantly reduce power loss at zero
load, especially when a Zener clamp is used. For very low
secondary power consumption use a TL431 regulator for
feedback control. Alternately, switching losses can be
significantly reduced by switching from 132 kHz in normal
operation to 66 kHz under light load conditions.
TOPSwitch-FX Layout Considerations
Primary Side Connections
Use a single point (Kelvin) connection at the negative terminal
of the input filter capacitor for TOPSwitch-FX SOURCE pin and
bias winding return. This improves surge capabilities by
returning surge currents from the bias winding directly to the
input filter capacitor.
The CONTROL pin bypass capacitor should be located as
close as possible to the SOURCE and CONTROL pins and its
SOURCE connection trace should not be shared by the main
MOSFET switching currents.
All SOURCE pin referenced components connected to the
MULTI-FUNCTION pin should also be located close to
SOURCE and MULTI-FUNCTION pins with dedicated
SOURCE pin connection. The MULTI-FUNCTION pin’s trace
should be kept as short as possible and away from the DRAIN
trace to prevent noise coupling. Line sense resistor (R1 in
Figures 29 and 30) should be located close to the MULTI-
FUNCTION pin to minimize the trace length on the MULTI-
FUNCTION pin side.
In addition to the 47 µF CONTROL pin capacitor, a high
frequency bypass capacitor in parallel may be used for better
noise immunity. The feedback optocoupler output should also
be located close to the CONTROL and SOURCE pins of
TOPSwitch-FX.
Y-Capacitor
The Y-capacitor should be connected close to the secondary
output return pin(s) and the primary DC input pin of the
transformer (see Figures 29 and 30).
Heat Sinking
The tab of the Y package (TO-220) is internally electrically
tied to the SOURCE pin. To avoid circulating currents, a heat
sink attached to the tab should not be electrically tied to any
nodes on the PC board.
When using P (DIP-8) or G (SMD-8) packages, a copper area
underneath the package connected to the SOURCE pins will
act as an effective heat sink.
In addition, sufficient copper area should be provided at the
anode and cathode leads of the output diode(s) for heat
sinking.
Quick Design Checklist
As with any power supply design, all TOPSwitch-FX designs
should be verified on the bench to make sure that components
specifications are not exceeded under worst case conditions.
The following minimum set of tests is strongly recommended:
1. Maximum drain voltage – Verify that peak VDS does not
exceed 675 V at highest input voltage and maximum
overload output power. Maximum overload output power
occurs when the ouput is overloaded to a level just before
the power supply goes into auto-restart (loss of regulation).
2. Maximum drain current – At maximum ambient
temperature, maximum input voltage and maximum output
load, verify drain current waveforms at start-up for any
signs of transformer saturation and excessive leading edge
current spikes. TOPSwitch-FX has a leading edge blanking
time of 200 ns to prevent premature termination of the
on-cycle. Verify that the leading edge current spike is
below the allowed current limit envelope (see Figure 33) for
the drain current waveform at the end of the 200 ns
blanking period.
3. Thermal check – At maximum output power, minimum
input voltage and maximum ambient temperature, verify
that temperature specifications are not exceeded for
TOPSwitch-FX, transformer, output diodes and output
capacitors. Enough thermal margin should be allowed for
the part-to-part variation of the RDS(ON) of TOPSwitch-FX as
specified in the data sheet. The margin required can either
be calculated from the tolerances or it can be accounted
for by connecting an external resistance in series with the
DRAIN pin and attached to the same heat sink, having a
resistance value that is equal to the difference between the
measured RDS(ON) of the device under test and the worst
case maximum specification.
Design Tools
1. Technical literature: Data Sheet, Application Notes, Design
Ideas, etc.
2. ransformer design spreadsheet.
3. Engineering prototype boards.
Up to date information on design tools can be found at Power
Integrations Web site: www.power.com
Rev. C 06/15
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TOP232-234
www.power.com
ABSOLUTE MAXIMUM RATINGS(1,4)
DRAIN Pin Voltage ........................................... -0.3 to 700 V
DRAIN Pin Peak Current: TOP232 ................................0.8 A
TOP233 ................................1.6 A
TOP234 ................................2.4 A
CONTROL Pin Voltage ......................................... -0.3 to 9 V
CONTROL Pin Current ..............................................100 mA
MULTI-FUNCTION Pin Voltage ............................. -0.3 to 9 V
FREQUENCY Pin Voltage ..................................... -0.3 to 9 V
Operating Junction Temperature(2) .................. -40 to 150 °C
IC = 4 mA;
TJ = 25 °C
IC = ICD1
fOSC
∆f
fM
DCMAX
DCMIN
tSOFT
CONTROL FUNCTIONS
Conditions
(Unless Otherwise Specified)
See Figure 34
SOURCE = 0 V; TJ = -40 to 125 °C
Min Typ Max
Parameter Symbol Units
THERMAL RESISTANCE
kHz
kHz
Hz
%
%
ms
%/mA
Thermal Resistance: Y Package
(θJA)(1) ...................................... 70 °C/W
(θJC)(2) ........................................ 2 °C/W
P/G Package:
(θJA) .....................45 °C/W(3); 35 °C/W(4)
(θJC)(5) ...................................... 11 °C/W
Notes:
1. Free standing with no heat sink.
2. Measured at the back surface of tab.
3. Soldered to 0.36 sq. inch (232 mm2), 2oz. (610 gm/m2) copper clad.
4. Soldered to 1 sq. inch (645 mm2), 2oz. (610 gm/m2) copper clad.
5. Measured on the SOURCE pin close to plastic interface.
124 132 140
61.5 66 70.5
± 4
± 2
250
75.0 78.0 82.0
35.0 47.0 57.0
0.8 1.5 2.7
10 14
-27 -22 -17
IC = 4 mA; TJ = 25 °C
Switching
Frequency
(average)
Frequency Jitter
Deviation
Frequency Jitter
Modulation Rate
Maximum Duty
Cycle
Minimum Duty
Cycle (Prior to
Cycle Skipping)
Soft Start Time
PWM
Gain
FREQUENCY Pin
Connected to SOURCE
FREQUENCY Pin
Connected to CONTROL
132 kHz Operation
66 kHz Operation
IM ≤ IM(DC)
IM = 190 µA
TJ = 25 °C; DCMIN to DCMAX
Lead Temperature(3) ................................................... 260 °C
Notes:
1. All voltages referenced to SOURCE, TA = 25 °C.
2. Normally limited by internal circuitry.
3. 1/16” from case for 5 seconds.
4. The Absolute Maximum Ratings specified may be applied,
one at a time without causing permanent damage to the
product. Exposure to Absolute Maximum Ratings for ex-
tended periods of time may affect product reliability.
Rev. C 06/15
25
TOP232-234
www.power.com
CONTROL FUNCTIONS (cont.)
Conditions
(Unless Otherwise Specified)
See Figure 34
SOURCE = 0 V; TJ = -40 to 125 °C
Min Typ Max
Parameter Symbol Units
See Note A
See Figure 4
TJ = 25 °C
IC = 4 mA; TJ = 25 °C
See Figure 32
lB
ZC
PWM Gain
Temperature Drift
External Bias
Current
CONTROL
Current at Start of
Cycle Skipping
Dynamic
Impedance
Dynamic
Impedance
Temperature Drift
Control Pin
Internal Filter Pole
%/mA/°C
mA
mA
Ω
%/°C
kHz
SHUTDOWN/AUTO-RESTART
VC = 0 V
VC = 5 V
lC (CH)
vC(AR)
Control Pin
Charging Current
Charging Current
Temperature Drift
Auto-restart Upper
Threshold Voltage
Auto-restart Lower
Threshold Voltage
Auto-restart
Hysteresis Voltage
Auto-restart Duty
Cycle
Auto-restart
Frequency
mA
%/°C
V
V
V
%
Hz
-5.0 -3.8 -2.6
-3.0 -1.9 -0.8
0.5
5.8
4.5 4.8 5.1
0.8 1.0
2 4 8
1.0
TJ = 25 °C
See Note A
- 0.01
1.2 1.9 2.8
5.9 7.5
10 15 22
0.18
7
Rev. C 06/15
26
TOP232-234
www.power.com
MULTI-FUNCTION INPUT
Conditions
(Unless Otherwise Specified)
See Figure 34
SOURCE = 0 V; TJ = -40 to 125 °C
Min Typ Max
Parameter Symbol Units
lUV
IOV
IREM (N)
IM (SC)
VM
IM (DC)
TRON
TROFF
µA
µA
µA
µA
µA
µA
V
µA
%/µA
mA
µs
µs
44 50 54
210 225 240
10
-43 -35 -27
-7
300 400 520
-300 -240 -180
-110 -90 -70
2.00 2.60 3.00
2.50 2.90 3.30
1.25 1.32 1.39
1.18 1.24 1.30
75 90 110
0.30
0.6 1.1
1.0 1.8
1.5 2.5 4.0
1.5 2.5 4.0
TJ = 25 °C
MULTI-FUNCTION
Pin Floating
MULTI-FUNCTION
Pin Shorted to
CONTROL
TJ = 25 °C
Threshold
Hysteresis
TJ = 25 °C
VM = VC
Normal Mode
Auto-restart Mode
lM = 50 µA
lM = 225 µA
lM = -50 µA
lM = -150 µA
TJ = 25 °C
IM > IM (DC)
VDRAIN = 150 V
From Remote On to Drain Turn-On
See Note B
Minimum Time Before Drain
Turn-On to Disable Cycle
See Note B
VM = 0 V
Threshold
Hysteresis
Line Undervoltage
Threshold Current
Line Overvoltage or
Remote ON/OFF
Threshold Current
and Hysteresis
Remote ON/OFF
Negative Threshold
Current and
Hysteresis
MULTI-FUNCTION
Pin Short Circuit
Current
MULTI-FUNCTION
Pin Voltage
Maximum Duty
Cycle Reduction
Onset Threshold
Current
Maximum Duty
Cycle Reduction
Slope
Remote-OFF
DRAIN Supply
Current
Remote-ON Delay
Remote-OFF
Setup Time
Rev. C 06/15
27
TOP232-234
www.power.com
ILIMIT
IINIT
tLEB
tILD
VC(RESET)
RDS(ON)
A
A
ns
ns
°C
°C
V
Ω
Conditions
(Unless Otherwise Specified)
See Figure 34
SOURCE = 0 V; TJ = -40 to 125 °C
Min Typ Max
Parameter Symbol Units
CIRCUIT PROTECTION
See Figure 33
TJ = 25 °C
TJ = 25 °C
TJ = 100 °C
TJ = 25 °C
TJ = 100 °C
TJ = 25 °C
TJ = 100 °C
TOP232
ID = 50 mA
TOP233
ID = 100 mA
TOP234
ID = 150 mA
OUTPUT
FREQUENCY INPUT
FREQUENCY Pin
Threshold Voltage
FREQUENCY Pin
Input Current VF = VC
VF
IF
0.465 0.500 0.535
0.930 1.000 1.070
1.395 1.500 1.605
0.75 x
ILIMIT(MIN)
0.6 x
ILIMIT(MIN)
200
100
125 135 150
70
2.0 3.3 4.3
15.6 18.0
25.7 30.0
7.8 9.0
12.9 15.0
5.2 6.0
8.6 10.0
Self Protection
Current Limit
Initial Current Limit
Leading Edge
Blanking Time
Current Limit Delay
Thermal Shutdown
Temperature
Thermal Shutdown
Hysteresis
Power-up Reset
Threshold Voltage
ON-State
Resistance
TOP232
TJ= 25 °C
TOP233
TJ= 25 °C
TOP234
TJ= 25 °C
≤ 85 VAC
(Rectified Line Input)
265 VAC
(Rectified Line Input)
IC = 4 mA
IC = 4 mA
Figure 34, S1 open
Internal; di/dt = 100mA/µs
Internal; di/dt = 200mA/µs
Internal; di/dt = 300mA/µs
See Note B 1.0 2.9 VC -1.0 V
10 22 40 µA
See Note C
See Note C
See Note C
Rev. C 06/15
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TOP232-234
www.power.com
100
50
36
5.60 5.85 6.10
±50
1.0 1.5 2.0
0.3 0.6 1.0
ns
ns
V
V
ppm/°C
mA
Conditions
(Unless Otherwise Specified)
See Figure 34
SOURCE = 0 V; TJ = -40 to 125 °C
Min Typ Max
Parameter Symbol Units
tR
tF
VC(SHUNT)
lCD1
lCD2
Measured in a Typical
Flyback Converter Application
See Note D
IC = 4 mA
Output
MOSFET Enabled
VM = 0 V
Output
MOSFET Disabled
VM = 0 V
SUPPLY VOLTAGE CHARACTERISTICS
OUTPUT (cont.)
Off-State
Current
Breakdown
Voltage
IDSS
BVDSS
150 µA
700 V
Rise Time
Fall Time
DRAIN Supply
Voltage
Shunt Regulator
Voltage
Shunt Regulator
Temperature Drift
Control Supply/
Discharge Current
VM = Floating; IC = 4mA
VDS = 560 V; TJ = 125 °C
VM = Floating; IC = 4mA
ID = 100 µA; TJ = 25 °C
NOTES:
A. For specifications with negative values, a negative temperature coefficient corresponds to an increase in magnitude
with increasing temperature, and a positive temperature coefficient corresponds to a decrease in magnitude with
increasing temperature.
B. Guaranteed by characterization. Not tested in production.
C. For externally adjusted current limit values, please refer to the graph (Current Limit vs. External Current Limit Resis-
tance) in the Typical Performance Characteristics section.
D. It is possible to start up and operate TOPSwitch-FX at DRAIN voltages well below 36 V. However, the CONTROL pin
charging current is reduced, which affects start-up time, auto-restart frequency, and auto-restart duty cycle. Refer to
the characteristic graph on CONTROL pin charge current (IC) vs. DRAIN voltage for low voltage operation characteristics.
Rev. C 06/15
29
TOP232-234
www.power.com
Figure 32. CONTROL Pin I-V Characteristic.
Figure 31. Duty Cycle Measurement.
Figure 33. Drain Current Operating Envelope.
Figure 34. TOPSwitch-FX General Test Circuit.
PI-2538-062615
5-50 V
S4
0-60 kΩ
40 V
0-15 V
0.1 µF47 µF
470 Ω
5 W
470 Ω
100 kΩ
NOTES: 1. This test circuit is not applicable for current limit or output characteristic measurements.
2. For P and G packages, short all SOURCE pins together.
D
SF
M
C
CONTROL
TOPSwitch-FX
S2
S3
S1
0.8
1.3
1.2
1.1
0.9
0.8
1.0
0
0 1 2 6 83
Time (µs)
DRAIN Current (normalized)
PI-2022-033015
4 5 7
0.7
0.6
0.5
0.4
0.3
0.2
0.1
I
LIMIT(MAX)
@ 25 ˚C
I
LIMIT(MIN)
@ 25 ˚C
I
INIT(MIN)
@ 85 VAC
I
INIT(MIN)
@ 265 VAC
tLEB (Blanking Time)
PI-2039-033001
DRAIN
VOLTAGE
HV
0 V
90%
10%
90%
t2
t1
D = t1
t2
120
100
80
40
20
60
0
0 2 4 6 8 10
CONTROL Pin Voltage (V)
CONTROL Pin Current (mA)
PI-1939-033015
1
Slope
Dynamic
Impedance =
Rev. C 06/15
30
TOP232-234
www.power.com
The following precautions should be followed when testing
TOPSwitch-FX by itself outside of a power supply. The
schematic shown in Figure 34 is suggested for laboratory
testing of TOPSwitch-FX.
When the DRAIN pin supply is turned on, the part will be in the
auto-restart mode. The CONTROL pin voltage will be
oscillating at a low frequency between 4.8 and 5.8 V and the
drain is turned on every eighth cycle of the CONTROL pin
oscillation. If the CONTROL pin power supply is turned on
BENCH TEST PRECAUTIONS FOR EVALUATION OF ELECTRICAL CHARACTERISTICS
Typical Performance Characteristics
while in this auto-restart mode, there is only a 12.5% chance
that the CONTROL pin oscillation will be in the correct state
(drain active state) so that the continuous drain voltage
waveform may be observed. It is recommended that the VC
power supply be turned on first and the DRAIN pin power
supply second if continuous drain voltage waveforms are to be
observed. The 12.5% chance of being in the correct state is
due to the divide-by-8 counter. Temporarily shorting the
CONTROL pin to the SOURCE pin will reset TOPSwitch-FX,
which then will come up in the correct state.
.3
.4
.5
.6
.7
.8
.9
1.0
-250 -200 -150 -100 -50 0
IM (µA)
Current Limit (A)
CURRENT LIMIT vs. MULTI-FUNCTION
PIN CURRENT
PI-2540-033001
60
80
100
120
140
160
180
200
di/dt (mA/µs)
TOP234 1.50
TOP233 1.00
TOP232 0.50
Scaling Factors:
.3
.4
.5
.6
.7
.8
.9
1.0
1.1
60
80
100
120
140
160
180
200
05K 10K 15K 20K 25K
External Current Limit Resistor R
IL
(Ω)
Current Limit (A)
di/dt (mA/µs)
CURRENT LIMIT vs. EXTERNAL
CURRENT LIMIT RESISTANCE
PI-2539-033001
30K
Maximum and minimum levels
are based on characterization.
Maximum
Minimum
Typical
TOP234 1.50
TOP233 1.00
TOP232 0.50
Scaling Factors:
Rev. C 06/15
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TOP232-234
www.power.com
Typical Performance Characteristics (cont.)
1.1
1.0
0.9
-50 -25 0255075 100 125 150
Junction Temperature (°C)
Breakdown Voltage
(Normalized to 25 °C)
BREAKDOWN vs. TEMPERATURE
PI-176B-033001
1.2
1.0
0.8
0.6
0.4
0.2
0
-50 -25 0255075 100 125 150
Junction Temperature (°C)
FREQUENCY vs. TEMPERATURE
PI-1123A-033001
Output Frequency
(Normalized to 25 °C)
Junction Temperature (°C)
OVER-VOLTAGE THRESHOLD
vs. TEMPERATURE
PI-2553-033001
Over-Voltage Threshold
(Normalized to 25
°C)
Junction Temperature (°C)
UNDER-VOLTAGE THRESHOLD
vs. TEMPERATURE
PI-2552-033001
Under-Voltage Threshold
(Normalized to 25 °C)
Junction Temperature (°C)
OVER-VOLTAGE THRESHOLD
vs. TEMPERATURE
PI-2553-033001
Over-Voltage Threshold
(Normalized to 25 °C)
Junction Temperature (°C)
UNDER-VOLTAGE THRESHOLD
vs. TEMPERATURE
PI-2552-033001
Under-Voltage Threshold
(Normalized to 25 °C)
Rev. C 06/15
32
TOP232-234
www.power.com
Typical Performance Characteristics (cont.)
1.2
1.4
1.6
0.4
0.6
0.2
0.8
1.0
0
-300 -200 -150 -50-250 -100 0
MULTI-FUNCTION Pin Voltage (V)
MULTI-FUNCTION PIN VOLTAGE
vs. CURRENT (EXPANDED)
PI-2541-091699
MULTI-FUNCTION Pin Current (mA)
6
5
4
3
2
1
0
-300 -200 -100 0 100 200 300 400 500
MULTI-FUNCTION PIN VOLTAGE
vs. CURRENT
PI-2542-091699
MULTI-FUNCTION Pin (V)
MULTI-FUNCTION Pin Current (µA)
See
Expanded
Version
2
1.2
1.6
0
020406080 100
DRAIN Voltage (V)
CONTROL Pin
Charging Current (mA)
IC vs. DRAIN VOLTAGE
PI-2564-101499
0.4
0.8
VC = 5 V
Junction Temperature (°C)
CONTROL CURRENT at START of
CYCLE SKIPPING vs. TEMPERATURE
PI-2562-033001
CONTROL Current
(Normalized to 25 °C)
Junction Temperature (°C)
MAX. DUTY CYCLE REDUCTION ONSET
THRESHOLD CURRENT vs. TEMPERATURE
PI-2563-033001
Onset Threshold Current
(Normalized to 25 °C)
1.5
0
02 46 810
DRAIN Voltage (V)
DRAIN Current (A)
OUTPUT CHARACTERISTICS
PI-1940-033001
0.5
T
CASE
= 25 °C
T
CASE
= 100 °C
1
TOP234 1.00
TOP233 0.67
TOP232 0.33
Scaling Factors:
Rev. C 06/15
33
TOP232-234
www.power.com
Typical Performance Characteristics (cont.)
1000
10
0 400200 600
DRAIN Voltage (V)
DRAIN Capacitance (pF)
COSS vs. DRAIN VOLTAGE
100
PI-1941-033001
TOP234 1.00
TOP233 0.67
TOP232 0.33
Scaling Factors:
200
300
100
0
0 200 400 600
DRAIN Voltage (V)
Power (mW)
DRAIN CAPACITANCE POWER (132 kHz)
PI-1942-033001
TOP234 1.00
TOP233 0.67
TOP232 0.33
Scaling Factors:
Rev. C 06/15
34
TOP232-234
www.power.com
Notes:
1. Controlling dimensions are inches. Millimeter
dimensions are shown in parentheses.
2. Pin locations start with Pin 1, and continue
from left to right when viewed from the front.
Pins 2 and 6 are omitted.
3. Dimensions do not include mold flash or
other protrusions. Mold flash or protrusions
shall not exceed .006 (.15mm) on any side.
4. Minimum metal to metal spacing at the pack-
age body for omitted pin locations is .068
inch (1.73 mm).
5. Position of the formed leads to be measured
at the mounting plane, .670 inch (17.02 mm)
below the hole center.
6. All terminals are solder plated.
Y07B MOUNTING HOLE PATTERN
.050 (1.27)
.150 (3.81)
.050 (1.27)
.150 (3.81)
.050 (1.27)
.050 (1.27)
.180 (4.58)
.200 (5.08)
.010 (.25) M
.467 (11.86)
.487 (12.37)
.400 (10.16)
.415 (10.54)
.146 (3.71)
.156 (3.96)
.860 (21.84)
.880 (22.35)
.028 (.71)
.032 (.81)
.050 (1.27) BSC
.150 (3.81) BSC
.108 (2.74) REF
7° TYP.
.040 (1.02)
.060 (1.52)
.190 (4.83)
.210 (5.33)
.015 (.38)
.020 (.51)
.095 (2.41)
.115 (2.92)
.236 (5.99)
.260 (6.60)
.165 (4.19)
.185 (4.70)
.040 (1.02)
.060 (1.52)
.045 (1.14)
.055 (1.40)
.670 (17.02)
REF.
.570 (14.48)
REF.
TO-220-7B
Rev. C 06/15
35
TOP232-234
www.power.com
Notes:
1. Package dimensions conform to JEDEC specification
MS-001-AB (Issue B 7/85) for standard dual-in-line (DIP)
package with .300 inch row spacing.
2. Controlling dimensions are inches. Millimeter sizes are
shown in parentheses.
3. Dimensions shown do not include mold flash or other
protrusions. Mold flash or protrusions shall not exceed
.006 (.15) on any side.
4. Pin locations start with Pin 1, and continue counter-clock-
wise to Pin 8 when viewed from the top. The notch and/or
dimple are aids in locating Pin 1. Pin 6 is omitted.
5. Minimum metal to metal spacing at the package body for
the omitted lead location is .137 inch (3.48 mm).
6. Lead width measured at package body.
7. Lead spacing measured with the leads constrained to be
perpendicular to plane T.
.008 (.20)
.015 (.38)
.300 (7.62) BSC
(NOTE 7)
.300 (7.62)
.390 (9.91)
.367 (9.32)
.387 (9.83)
.240 (6.10)
.260 (6.60)
.125 (3.18)
.145 (3.68)
.057 (1.45)
.068 (1.73)
.120 (3.05)
.140 (3.56)
.015 (.38)
MINIMUM
.048 (1.22)
.053 (1.35)
.100 (2.54) BSC
.014 (.36)
.022 (.56)
-E-
Pin 1
SEATING
PLANE
-D-
-T-
P08B
PDIP-8B (P Package)
PI-2551-040110
D S .004 (.10)
⊕
T E D S .010 (.25) M
⊕
(NOTE 6)
.137 (3.48)
MINIMUM
SMD-8B (G Package)
PI-2546-040110
.004 (.10)
.012 (.30)
.036 (0.91)
.044 (1.12)
.004 (.10)
0 -
°
8
°
.367 (9.32)
.387 (9.83)
.048 (1.22) .009 (.23)
.053 (1.35)
.032 (.81)
.037 (.94)
.125 (3.18)
.145 (3.68)
-D-
Notes:
1. Controlling dimensions are
inches. Millimeter sizes are
shown in parentheses.
2. Dimensions shown do not
include mold flash or other
protrusions. Mold flash or
protrusions shall not exceed
.006 (.15) on any side.
3. Pin locations start with Pin 1,
and continue counter-clock-
wise to Pin 8 when viewed
from the top. Pin 6 is omitted.
4. Minimum metal to metal
spacing at the package body
for the omitted lead location
is .137 inch (3.48 mm).
5. Lead width measured at
package body.
6. D and E are referenced
datums on the package
body.
.057 (1.45)
.068 (1.73)
(NOTE 5)
E S
.100 (2.54) (BSC)
.372 (9.45)
.240 (6.10) .388 (9.86)
.137 (3.48)
MINIMUM
.260 (6.60) .010 (.25)
-E-
Pin 1
D S .004 (.10)
⊕
⊕
G08B
.420
.046 .060 .060 .046
.080
Pin 1
.086
.186
.286
Solder Pad Dimensions
Rev. C 06/15
36
TOP232-234
www.power.com
Revision Notes Date
A Initial Release. 01/00
BCorrected rounding of operating frequency (132/66 kHz), corrected spelling and corrected Storage Temperature θJC and
updated nomenclature in parameter table. 07/01
C Updated with new Brand Style Logo. 06/15
For the latest updates, visit our website: www.power.com
Power Integrations reserves the right to make changes to its products at any time to improve reliability or manufacturability. Power
Integrations does not assume any liability arising from the use of any device or circuit described herein. POWER INTEGRATIONS MAKES
NO WARRANTY HEREIN AND SPECIFICALLY DISCLAIMS ALL WARRANTIES INCLUDING, WITHOUT LIMITATION, THE IMPLIED
WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, AND NON-INFRINGEMENT OF THIRD PARTY RIGHTS.
Patent Information
The products and applications illustrated herein (including transformer construction and circuits external to the products) may be covered
by one or more U.S. and foreign patents, or potentially by pending U.S. and foreign patent applications assigned to Power Integrations.
A complete list of Power Integrations patents may be found at www.power.com. Power Integrations grants its customers a license under
certain patent rights as set forth at http://www.power.com/ip.htm.
Life Support Policy
POWER INTEGRATIONS PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR
SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF POWER INTEGRATIONS. As used herein:
1. A Life support device or system is one which, (i) is intended for surgical implant into the body, or (ii) supports or sustains life, and (iii)
whose failure to perform, when properly used in accordance with instructions for use, can be reasonably expected to result in significant
injury or death to the user.
2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause
the failure of the life support device or system, or to affect its safety or effectiveness.
The PI logo, TOPSwitch, TinySwitch, LinkSwitch, LYTSwitch, InnoSwitch, DPA-Switch, PeakSwitch, CAPZero, SENZero, LinkZero,
HiperPFS, HiperTFS, HiperLCS, Qspeed, EcoSmart, Clampless, E-Shield, Filterfuse, FluxLink, StakFET, PI Expert and PI FACTS are
trademarks of Power Integrations, Inc. Other trademarks are property of their respective companies. ©2014, Power Integrations, Inc.
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