June 2009
© 2009 Fairchild Semiconductor Corporation www.fairchildsemi.com
FAN6961 • Rev. 1.0.3
FAN6961 —Boundary Mode PFC Controller
FAN6961
Boundary Mode PFC Controller
Features
Boundary Mode PFC Controller
Low Input Current THD
Controlled On-Time PWM
Zero-Current Detection
Cycle-by-Cycle Current Limiting
Leading-Edge Blanking instead of RC Filtering
Low Startup Current: 10µA Typical
Low Operating Current: 4.5mA Typical
Feedback Open-Loop Protection
Programmable Maximum On-Time (MOT)
Output Over-Voltage Clamping Protection
Clamped Gate Output Voltage 16.5V
Applications
Electric Lamp Ballasts
AC-DC Switching Mode Power Converter
Open Frame Power Supplies and Power Adapters
Flyback Power Converters with ZCS / ZVS
Description
The FAN6961 is an 8-pin, boundary-mode, PFC
controller IC intended for controlling PFC pre-
regulators. The FAN6961 provides a controlled on-time
to regulate the output DC voltage and achieve natural
power factor correction. The maximum on-time of the
external switch is programmable to ensure safe
operation during AC brownouts. An innovative multi-
vector error amplifier is built in to provide rapid transient
response and precise output voltage clamping. A built-
in circuit disables the controller if the output feedback
loop is opened. The startup current is lower than 20µA
and the operating current has been reduced to under
6mA. The supply voltage can be up to 25V, maximizing
application flexibility.
Ordering Information
Part
Number Operating
Temperature Range Package Eco Status Packing
Method
FAN6961SZ -40°C to +125°C 8-Pin, Small Outline Package (SOP) RoHS Tape & Reel
FAN6961DZ -40°C to +125°C 8-Pin, Dual In-line Package (DIP) RoHS Tube
FAN6961SY -40°C to +125°C 8-Pin, Small Outline Package (SOP) Green Tape & Reel
For Fairchild’s defini t i on of Eco St atus, pleas e visit: http://www.fairchildsemi.com/company/green/rohs_green.html.
© 2009 Fairchild Semiconductor Corporation www.fairchildsemi.com
FAN6961 • Rev. 1.0.3 2
FAN6961 — Boundary Mode PFC Controller
Application Diagram
Figure 1. Typical Application
Block Diagram
Figure 2. Function Block Diagram
© 2009 Fairchild Semiconductor Corporation www.fairchildsemi.com
FAN6961 • Rev. 1.0.3 3
FAN6961 — Boundary Mode PFC Controller
Marking Informa ti on
Figure 3. Marking Information
Pin Configuration
1432
8765
VCC GATE
MOT
ZCD
INV COMP CS
GND
Figure 4. DIP and SOP Pin Configuration (Top View)
Pin Definitions
Pin # Name Description
1 INV
Inverting Input of the Error Amplifier. INV is connected to the converter output via a resistive
divider. This pin is also used for over-voltage clamping and open-loop feedback protection.
2 COMP
Output of the Error Amplifier. To create a precise clamping protection, a compensation
network between this pin and GND is suggested.
3 MOT
Maximum On Time. A resistor from MOT to GND is used to determine the maximum on-time of
the external power MOSFET. The maximum output power of the converter is a function of the
maximum on time.
4 CS
Current Sense. Input to the over-current protection comparator. When the sensed voltage
across the sense resistor reaches the internal threshold (0.8V), the switch is turned off to
activate cycle-by-cycle current limiting.
5 ZCD
Zero Current Detection. This pin is connected to an auxiliary winding via a resistor to detect
the zero crossing of the switch current. When the zero crossing is detected, a new switching
cycle is started. If it is connected to GND, the device is disabled.
6 GND
Ground. The power ground and signal ground. Placing a 0.1µF decoupling capacitor between
VCC and GND is recommended.
7 GATE
Driver Output. Totem-pole driver output to drive the external power MOSFET. The clamped
gate output voltage is 16.5V.
8 VCC
Power Supply. Driver and control circuit supply voltage.
F- Fairchild Logo
Z- Plant Code
X- Year Code
Y- Week Code
TT: Die Run Code
T: Package Type (S=SOP, D=DIP)
P: Z: Pb Free Y: Green Compound
M: Manufacture Flow Code
FAN6961
TPM
© 2009 Fairchild Semiconductor Corporation www.fairchildsemi.com
FAN6961 • Rev. 1.0.3 4
FAN6961 — Boundary Mode PFC Controller
Absolute Maximum Ratings
Stresses exceeding the absolute maximum ratings may damage the device. The device may not function or be
operable above the recommended operating conditions and stressing the parts to these levels is not recommended.
In addition, extended exposure to stresses above the recommended operating conditions may affect device
reliability. The absolute maximum ratings are stress ratings only. All voltage values, except differential voltage, are
given with respect to GND pin.
Symbol Parameter Min. Max. Unit
VVCC DC Supply Voltage 30 V
VHIGH Gate Driver -0.3 30.0 V
VLOW Others (INV, COMP, MOT, CS) -0.3 7.0 V
VZCD Input Voltage to ZCD Pin -0.3 12.0 V
SOP 400
PD Power Dissipation DIP 800 mW
TJ Operating Junction Temperature -40 +125 °C
SOP 150
θJA Thermal Resistance (Junction-to-Air) DIP 113 °C/W
TSTG Storage Temperature Range -65 +150 °C
SOP +230
TL Lead Temperature (Wave Soldering or IR, 10 Seconds) DIP +260 °C
Human Body Model: JESD22-A114 2.5 KV
ESD Machine Model: JESD22-A115 200 V
Recommended Operating Conditions
The Recommended Operating Conditions table defines the conditions for actual device operation. Recommended
operating conditions are specified to ensure optimal performance to the datasheet specifications. Fairchild does not
recommend exceeding them or designing to Absolute Maximum Ratings.
Symbol Parameter Min. Typ. Max. Unit
TA Operating Ambient Temperature -40 +125 °C
© 2009 Fairchild Semiconductor Corporation www.fairchildsemi.com
FAN6961 • Rev. 1.0.3 5
FAN6961 — Boundary Mode PFC Controller
Electrical Characteristics
Unless otherwise noted, VCC=15V and TJ= -40°C to 125°C. Current is defined as positive into the device and
negative out of the device.
Symbol Parameter Conditions Min. Typ. Max. Units
VCC Section
VCC-OP Continuous Operation Voltage 24.5 V
VCC-ON Turn-On Threshold Voltage 11.5 12.5 13.5 V
VCC-OFF Turn-Off Threshold Voltage 8.5 9.5 10.5 V
ICC-ST Startup Current VCC=VCC-ON – 0.16V 10 20 µA
ICC-OP Operating Supply Current VCC=12V, VCS=0V,
CL=3nF, fSW=60KHz 4.5 6 mA
VCC-OVP V
DD Over-Voltage Protection Level 26.8 27.8 28.8 V
tD-VCCOVP V
DD Over-Voltage Protection Debounce 30 µs
Error Amplifier Section
VREF Reference Voltage 2.475 2.500 2.525 V
Gm Transconductance 125 μmho
VINVH Clamp High Feedback Voltage 2.65 2.70 V
VINVL Clamp Low Feedback Voltage 2.25 2.30 V
VOUT HIGH Output High Voltage 4.8 V
VOZ Zero Duty Cycle Output Voltage 1.15 1.25 1.35 V
VINV-OVP Over Voltage Protection for INV Input 2.70 2.75 2.80 V
VINV-UVP Under Voltage Protection for INV Input 0.40 0.45 0.50 V
VINV=2.35V, VCOMP=1.5V 10 20
Source Current
VINV=1.5V, 550 800
ICOMP
Sink Current VINV=2.65V, VCOMP=5V 10 20
μA
Current-Sense Section
VPK Threshold Voltage for Peak Current Limit
Cycle-by-Cycle Limit 0.77 0.82 0.87 V
tPD Propagation Delay 200 ns
RMOT=24k, VCOMP=5V 400 500
tLEB Leading-Edge Blanking Time RMOT=24k,
VCOMP=VOZ+50mV 270 350
ns
Gate Section
VZ-OUT Output Voltage Maximum (Clamp) VCC=25V 14.5 16.0 17.5 V
VOL Output Voltage Low VCC=15V, IO=100mA 1.4 V
VOH Output Voltage High VCC=14V, IO=100mA 8 V
tR Rising Time VCC=12V, CL=3nF,
20~80% 80 ns
tF Falling Time VCC=12V, CL=3nF,
80~20% 40 ns
Continued on the following page…
© 2009 Fairchild Semiconductor Corporation www.fairchildsemi.com
FAN6961 • Rev. 1.0.3 6
FAN6961 — Boundary Mode PFC Controller
Electrical Characteristics
Unless otherwise noted, VCC=15V and TJ=-40°C to 125°C. Current is defined as positive into the device and negative
out of the device.
Symbol Parameter Conditions Min. Typ. Max. Units
Zero Current Detection Section
VZCD Input Threshold Voltage Rising Edge VZCD Increasing 1.9 2.1 2.3 V
HYS of
VZCD Threshold Voltage Hysteresis VZCD Decreasing 0.35 V
VZCD-HIGH Upper Clamp Voltage IZCD=3mA 12 V
VZCD-LOW Lower Clamp Voltage IZCD=-1.5mA 0.3 V
tDEAD Maximum Delay, ZCD to Output Turn-On VCOMP=5V,
fSW=60KHz 100 400 ns
tRESTART Restart Time Output Turned Off by
ZCD 300 500 700 μs
tINHIB Inhibit Time (Maximum Switching
Frequency Limit) RMOT=24k 2.8 μs
VDIS Disable Threshold Voltage 130 200 250 mV
tZCD-DIS Disable Function Debounce Time RMOT=24k,
VZCD=100mV 800 μs
Maximum On Time Section
VMOT Maximum On Time Voltage 1.25 1.30 1.35 V
tON-MAX Maximum On Time Programming
(Resistor Based)
RMOT=24k, VCS=0V,
VCOMP=5V 25 μs
© 2009 Fairchild Semiconductor Corporation www.fairchildsemi.com
FAN6961 • Rev. 1.0.3 7
FAN6961 — Boundary Mode PFC Controller
Typical Performance Characteristics
2.475
2.485
2.495
2.505
2.515
2.525
-40 -25 -10 5 20 35 50 65 80 95 110 125
Temperature ()
V
ref
(V)
0.0
0.6
1.2
1.8
2.4
3.0
-40 -25 -10 5 20 35 50 65 80 95 110 125
Temperature ()
I
CC-OP
(mA)
Figure 5. VREF vs. TA Figure 6. ICC-OP vs. TA
24.20
24.28
24.36
24.44
24.52
24.60
-40 -25 -10 5 20 35 50 65 80 95 110 125
Temperature ()
t
ON-MAX
(μs)
11.0
11.6
12.2
12.8
13.4
14.0
-40 -25 -10 5 20 35 50 65 80 95 110 125
Temperature ()
V
th-ON
(V)
Figure 7. tON-MAX vs. TA Figure 8. Vth-ON vs. TA
8.5
8.9
9.3
9.7
10.1
10.5
-40 -25 -10 5 20 35 50 65 80 95 110 125
Temperature ()
V
th-OFF
(V)
4.0
6.4
8.8
11.2
13.6
16.0
-40 -25 -10 5 20 35 50 65 80 95 110 125
Temperature ()
I
CC-ST
(μA)
Figure 9. Vth-OFF vs. TA Figure 10. ICC-ST vs. TA
© 2009 Fairchild Semiconductor Corporation www.fairchildsemi.com
FAN6961 • Rev. 1.0.3 8
FAN6961 — Boundary Mode PFC Controller
Typical Performance Characteristics (Continued)
1.250
1.270
1.290
1.310
1.330
1.350
-40 -25 -10 5 20 35 50 65 80 95 110 125
Temperature ()
V
MOT
(V)
15.0
15.6
16.2
16.8
17.4
18.0
-40 -25 -10 5 20 35 50 65 80 95 110 125
Temperature ()
V
Z-OUT
(V)
Figure 11. VMOT vs. TA Figure 12. VZ-OUT vs. TA
0.77
0.79
0.81
0.83
0.85
0.87
-40 -25 -10 5 20 35 50 65 80 95 110 125
Temperature ()
V
PK
(V)
Figure 13. VPK vs. TA
© 2009 Fairchild Semiconductor Corporation www.fairchildsemi.com
FAN6961 • Rev. 1.0.3 9
FAN6961 — Boundary Mode PFC Controller
Functional Description
Error Amplifier
The inverting input of the error amplifier is referenced to
INV. The output of the error amplifier is referenced to
COMP. The non-inverting input is internally connected
to a fixed 2.5V ± 2% voltage. The output of the error
amplifier is used to determine the on-time of the PWM
output and regulate the output voltage. To achieve a
low input current THD, the variation of the on time
within one input AC cycle should be very small. A multi-
vector error amplifier is built in to provide fast transient
response and precise output voltage clamping.
For FAN6961, connecting a capacitance, such as 1µF,
between COMP and GND is suggested. The error
amplifier is a trans-conductance amplifier that converts
voltage to current with a 125µmho.
Startup Current
Typical startup current is less than 20µA. This ultra-low
startup current allows the usage of high resistance,
low-wattage startup resistor. For example, 1M/0.25W
startup resistor and a 10µF/25V (VCC hold-up) capacitor
are recommended for an AC-to-DC power adaptor with
a wide input range 85-265VAC.
Operating Current
Operating current is typically 4.5mA. The low operating
current enables a better efficiency and reduces the
requirement of VCC hold-up capacitance.
Maximum On-Time Operat i on
Given a fixed inductor value and maximum output
power, the relationship between on-time and line
voltage is:
η
=2
2
rms
o
on VPL
t (1)
If the line voltage is too low or the inductor value is too
high, tON is too long. To avoid extra low operating
frequency and achieve brownout protection, the
maximum value of tON is programmable by one resistor,
RI, connected between MOT and GND. A 24k resistor
RI generates corresponds to 25µs maximum on time:
()
skRt Ion
μ
24
25
)(
(max) Ω= (2)
The range of the maximum on-time is designed as 10 ~
50µs.
Peak Current Limit i ng
The switch current is sensed by one resistor. The
signal is feed into CS pin and an input terminal of a
comparator. A high voltage in CS pin terminates a
switching cycle immediately and cycle-by-cycle current
limit is achieved. The designed threshold of the
protection point is 0.82V.
Leading-Edge Blanking (LEB)
A turn-on spike on CS pin appears when the power
MOSFET is switched on. At the beginning of each
switching pulse, the current-limit comparator is disabled
for around 400ns to avoid premature termination. The
gate drive output cannot be switched off during the
blanking period. Conventional RC filtering is not
necessary, so the propagation delay of current limit
protection can be minimized.
Under-Voltage Lockout ( UVLO )
The turn-on and turn-off threshold voltage is fixed
internally at 12V/9.5V. This hysteresis behavior
guarantees a one-shot startup with proper startup
resistor and hold-up capacitor. With an ultra-low startup
current of 20µA, one 1M R
IN is sufficient for startup
under low input line voltage, 85Vrms. Power dissipation
on RIN would be less than 0.1W even under high line
(VAC=265Vrms) condition.
Output Driver
With low on resistance and high current driving
capability, the output driver can drive an external
capacitive load larger than 3000pF. Cross conduction
current has been avoided to minimize heat dissipation,
improving efficiency and reliability. This output driver is
internally clamped by a 16.5V Zener diode.
Zero-Current Detecti on (ZCD)
The zero-current detection of the inductor is achieved
using its auxiliary winding. When the stored energy of
the inductor is fully released to output, the voltage on
ZCD goes down and a new switching cycle is enabled
after a ZCD trigger. The power MOSFET is always
turned on with zero inductor current such that turn-on
loss and noise can be minimized. The converter works
in boundary-mode and peak inductor current is always
exactly twice of the average current. A natural power
factor correction function is achieved with the low-
bandwidth, on-time modulation. An inherent maximum
off time is built in to ensure proper start-up operation.
This ZCD pin can be used as a synchronous input.
Noise Immunit y
Noise on the current sense or control signal can cause
significant pulse-width jitter, particularly in the
boundary-mode operation. Slope compensation and
built-in debounce circuit can alleviate this problem.
Because the FAN6961 has a single ground pin, high
sink current at the output cannot be returned
separately. Good high-frequency or RF layout practices
should be followed. Avoiding long PCB traces and
component leads, locating compensation and filter
components near to the FAN6961, and increasing the
power MOSFET gate resistance improve performance.
© 2009 Fairchild Semiconductor Corporation www.fairchildsemi.com
FAN6961 • Rev. 1.0.3 10
FAN6961 — Boundary Mode PFC Controller
Reference Circuit
Figure 14. Reference Circuit
© 2009 Fairchild Semiconductor Corporation www.fairchildsemi.com
FAN6961 • Rev. 1.0.3 11
FAN6961 —Boundary Mode PFC Controller
Physical Dimensions
5.08 MAX
0.33 MIN
2.54
7.62
0.56
0.355
1.65
1.27
3.683
3.20
3.60
3.00
6.67
6.096
9.83
9.00
7.62
9.957
7.87
0.356
0.20
NOTES: UNLESS OTHERWISE SPECIFIED
A) THIS PACKAGE CONFORMS TO
JEDEC MS-001 VARIATION BA
B) ALL DIMENSIONS ARE IN MILLIMETERS.
C) DIMENSIONS ARE EXCLUSIVE OF BURRS,
MOLD FLASH, AND TIE BAR EXTRUSIONS.
D) DIMENSIONS AND TOLERANCES PER
ASME Y14.5M-1994
8.255
7.61
E) DRAWING FILENAME AND REVSION: MKT-N08FREV2.
(0.56)
Figure 15. 8-Lead, PDIP, JEDEC MS-001, .300 Inch Wide
Pack age drawings are provided as a service to customers consideri ng Fai rchild components . Drawings may c hange i n any manner
without notice. P l ease note the revi sion and/or date on t he drawing and contac t a Fairchild S emiconductor represent ative to v er ify
or obtain the most recent revi sion. Pac kage specif i cations do not expand the terms of Fai rchild’s worldwi de terms and condition s,
specifically the warranty t herei n, which covers Fairc hi l d products.
Always vis i t Fairchild S emiconductor’s online packaging area for the most recent package drawings:
http://www.fairchildsemi.com/packaging/.
© 2009 Fairchild Semiconductor Corporation www.fairchildsemi.com
FAN6961 • Rev. 1.0.3 12
FAN6961 —Boundary Mode PFC Controller
Physical Dimensions (Continued)
SEE DETAIL A
NOTES: UNLESS OTHERWISE SPECIFIED
A) THIS PACKAGE CONFORMS TO JEDEC
MS-012, VARIATION AA, ISSUE C,
B) ALL DIMENSIONS ARE IN MILLIMETERS.
C) DIMENSIONS DO NOT INCLUDE MOLD
FLASH OR BURRS.
D) LANDPATTERN STANDARD: SOIC127P600X175-8M.
E) DRAWING FILENAME: M08AREV13
LAND PATTERN RECOMMENDATION
SEATING PLANE
0.10 C
C
GAGE PLANE
x 45°
DETAIL A
SCALE: 2:1
PIN ONE
INDICATOR
4
8
1
C
MBA0.25
B
5
A
5.60
0.65
1.75
1.27
6.20
5.80
3.81
4.00
3.80
5.00
4.80
(0.33)
1.27
0.51
0.33
0.25
0.10
1.75 MAX
0.25
0.19
0.36
0.50
0.25
R0.10
R0.10
0.90
0.406 (1.04)
OPTION A - BEVEL EDGE
OPTION B - NO BEVEL EDGE
Figure 16. 8-Lead, SOIC,JEDEC MS-012, .150 Inch Narrow Body
Pack age drawings are provided as a service to customers consideri ng Fai rchild components . Drawings may c hange i n any manner
without notice. P l ease note the revi sion and/or date on t he drawing and contac t a Fairchild S emiconductor representative to verify
or obtain the most recent revi sion. Pac kage specif i cations do not expand the terms of Fai rchild’s worldwi de terms and condition s,
specifically the warranty t herei n, which covers Fairc hi l d products.
Always vis i t Fairchild S emiconductor’s online packaging area for the most recent package drawings:
http://www.fairchildsemi.com/packaging/.
© 2009 Fairchild Semiconductor Corporation www.fairchildsemi.com
FAN6961 • Rev. 1.0.3 13
FAN6961 —Boundary Mode PFC Controller