Philips Semiconductors Product specification
NE/SE5561Switched-mode power supply control circuit
1
1994 Aug 31 853-0889 13721
DESCRIPTION
The NE5561/SE5561 is a control circuit for use in switched-mode
power supplies. It contains an internal temperature- compensated
supply, PWM, sawtooth oscillator, overcurrent sense latch, and
output stage. The device is intended for low cost SMPS applications
where extensive housekeeping functions are not required.
FEATURES
•Micro-miniature (D) package
•Pulse-width modulator
•Current limiting (cycle-by-cycle)
•Sawtooth generator
•Stabilized power supply
•Double pulse protection
•Internal temperature-compensated reference
PIN CONFIGURATION
D, FE, N Packages
1
2
3
4 5
6
7
8
VCC
VZ
FEEDBACK
GAIN
GND
OUTPUT
CURRENT SENSE
RT, CT
Figure 1. Pin Configuration
APPLICATIONS
•Switched-mode power supplies
•DC motor controller inverter
•DC/DC converter
ORDERING INFORMATION
DESCRIPTION TEMPERATURE RANGE ORDER CODE DWG #
8-Pin Plastic Dual In-Line Package (DIP) 0 to +70°C NE5561N SOT97-1
8-Pin Plastic Dual In-Line Package (DIP) -55 to +125°C SE5561N SOT97-1
8-Pin Ceramic Dual In-Line Package (CERDIP) -55 to +125°C SE5561FE 0580A
8-Pin Small Outline (SO) Package 0 to +70°C NE5561D SOT96-1
BLOCK DIAGRAM
REF
VOLTAGE SAWTOOTH
GENERATOR
PWM
ERROR
AMP
FEEDBACK
GAIN
0.5V
CURRENT
SENSE
LATCH
S
R
GND
8.2V
OUTPUT
STABILIZED
SUPPLY
18
2
+
7
5
3
4
6
–
+
–
VCC
VZ
RT, CT
VCC
SL00385
Figure 2. Block Diagram
Philips Semiconductors Product specification
NE/SE5561Switched-mode power supply control circuit
1994 Aug 31 2
ABSOLUTE MAXIMUM RATINGS
SYMBOL PARAMETER RATING UNIT
VCC Supply1
Voltage-forced mode +18 V
Current-fed mode 30 mA
Output transistor (at 20-30V max)
IOUT Output current 40 mA
VOUT Output voltage VCC+1.4V V
Output duty cycle 98 %
PDMaximum total power dissipation 0.75 W
TAOperating temperature range
SE5561 -55 to +125 °C
NE5561 0 to 70 °C
NOTES:
1. See Voltage-Current-fed supply characteristic curve.
DC ELECTRICAL CHARACTERISTICS
VCC=12V, TA=25°C, unless otherwise specified.
SYMBOL
PARAMETER
TEST CONDITIONS
SE5561 NE5561
UNIT
SYMBOL
PARAMETER
TEST CONDITIONS
Min Typ Max Min Typ Max
UNIT
Reference section
VREF Internal ref voltage TA=25°C 3.69 3.75 3.84 3.57 3.75 3.96 V
Over temperature 3.65 3.88 3.55 3.98 V
VZInternal zener ref *IL=7mA 7.8 8.2 8.8 7.8 8.2 8.8 V
Temp. coefficient of VREF ±100 ±100 ppm/°C
Temp. coefficient of VZ±200 ±200 ppm/°C
Oscillator section
Frequency range Over temperature 50 100k 50 100k Hz
Initial accuracy RT and CT constant 5 5 %
Duty cycle range fO=20kHz 0 98 0 98 %
Current limiting
IIN Input current Pin 6=250mV TA=25°C -2 -10 -2 -10 µA
Over temp. -20 -20 µA
Single pulse inhibit delay Inhibit delay
time for 20%
overdrive at IOUT=20mA 0.88 1.10 0.88 1.10 µs
IOUT=40mA 0.7 0.8 0.7 0.8 µs
Current limit trip level .400 .500 .600 .400 .500 .600 V
Error amplifier
Open-loop gain 60 60 dB
Feedback resistor 10k 10k Ω
BW Small-signal bandwidth 3 3 MHz
VOH Output voltage swing 6.2 6.2 V
VOL Output voltage swing 0.7 0.7 V
Output stage
IOUT Output current Over temperature 20 20 mA
VCE Sat IC=20mA, Over temp. 0.4 0.4 V
Philips Semiconductors Product specification
NE/SE5561Switched-mode power supply control circuit
1994 Aug 31 3
DC ELECTRICAL CHARACTERISTICS
VCC=12V, TA=25°C, unless otherwise specified.
SYMBOL
PARAMETER
TEST CONDITIONS
SE5561 NE5561
UNIT
SYMBOL
PARAMETER
TEST CONDITIONS
Min Typ Max Min Typ Max
UNIT
Supply voltage/current
ICC
Supply current
IZ=0,
voltage-forced
TA=25°C 10.0 10.0
mA
ICC
Supply current
IZ=0,
voltage-forced
Over temp. 13.0 13.0
mA
VCC
Supply voltage
ICC=10mA, current-fed 20.0 21.0 22.0 19.0 21.0 24.0
V
VCC
Supply voltage
ICC=30mA current 20.0 30.0 20.0 30.0
V
Low supply protection
Pin 1 threshold 8 9 10.5 8 9 10.5 V
Philips Semiconductors Product specification
NE/SE5561Switched-mode power supply control circuit
1994 Aug 31 4
TYPICAL PERFORMANCE CHARACTERISTICS
GAIN (dB)
C (nF)
max is a function of f R2
R1 R2 VZVBEQ1
Error Amplifier
Open-Loop Gain Error Amplifier
Open-Loop Phase Transfer Curve of Pulse-Width
Modulator Duty Cycle vs Input Voltage
Power Derating Curve Typical Frequency Plot vs RT and CT
Maximum Duty Cycle vs
Base Voltage on Q1 Start-Up Circuit Slow-Start Voltage
100
90
80
70
60
50
40
30
20
10
00 1 2 3 4 5
V1
MAXIMUM DUTY CYCLE (%)
δ MAX (%) V4
t
t = R’C
2
4
Q1
R2
V1
C
R1 NE5561
VZ
2
5
NE5561
RT
CT
1.25
1.00
0.75
0.50
0.25
025 50 70 100 125 150
TOTAL PWR DISSIPATION (WATTS)
NE
SE
AMBIENT TEMPERATURE (°C)
PT = VCC ICC + (VCC – VZ) IZ
+ [V7 I7 x DUTY CYCLE]
100
90
80
70
60
50
40
30
20
10
00 1 2 3 4 5 6
V4
(%)
δ
1000
100
50
30
20
10
5
3
2
1
2 2.5 3 3.5 4 4.5
f (kHz)
R=10kΩ
R=20kΩ
R=40kΩ
R=5kΩ
60
50
40
30
20
10
01k 10k 100k 1M 10M
FREQUENCY (Hz)
PHASE ANGLE (DEG)
0
1k 10k 100k 1M 10M
FREQUENCY (Hz)
–30
–60
–90
–120
–150
–180
SL00386
Figure 3. Typical Performance Characteristics
Philips Semiconductors Product specification
NE/SE5561Switched-mode power supply control circuit
1994 Aug 31 5
RVCC +
VS*VCC
(10 20mA)
NOTE:
See DC Electrical Characteristics for Current Fed VCC Range.
NE5561 Voltage-Current-Fed
Supply Characteristics
Current-Fed Dropping Resistor
VS
RVCC
VCC
GND
1
8
mA
20
10
00 10 20 30 V
SL00387
Figure 4. NE5561 Voltage-Current-Fed Supply Characteristics
NE5561 START-UP
The start-up, or initial turn-on, of this device requires some degree of
external protective duty cycle limiting to prevent the duty cycle from
initially going to the extreme maximum (δ>90%). Either overcurrent
limit or slow-start circuitry must be employed to limit duty cycle to a
safe value during start-up. Both may be used, if desired.
To implement slow-start, the start-up circuit can be used. The divider
R1 and R2 sets a voltage, buffered by Q1, such that the output of
the error amplifier is clamped to a maximum output voltage, thereby
limiting the maximum duty cycle. The addition of capacitor C will
cause this voltage to ramp-up slowly when power is applied, causing
the duty cycle to ramp-up simultaneously.
Overcurrent limit may be used also. To limit duty cycle in this mode,
the switch current is monitored at Pin 6 and the output of the 5561 is
disabled on a cycle-by-cycle basis when current reaches the
programmed limit. With current limit control of slow-start, the duty
cycle is limited to that value, just allowing maximum switch current
to flow. (Approximately 0.50V measured at Pin 6.)
APPLICATIONS
5V, 0.5A Buck Regulator Operates from 15V
The converter design shows how simple it is to derive a TTL supply
from a system supply of 15V (see Figure 1). The NE5561 drives a
2N4920 PNP transistor directly to provide switching current to the
inductor.
Overall line regulation is excellent and covers a range of 12V to 18V
with minimal change (<10mV) in the output operating at full load.
As with all NE5561 circuits, the auxiliary slow start and δMAX circuit
is required, as evidenced by Q1. The δMAX limit may be calculated
by using the relationship:
R2
R1 )R2(8.2V) +VMAX
The maximum duty cycle is then determined from the pulse-width
modulator transfer graph, with R1 and R2 being defined from the
desired conditions.
