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Philips Semiconductors
Product specification
Switched-mode power supply control circuit
NE/SE5561
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.
PIN CONFIGURATION
D, FE, N Packages
VCC VZ
1 2 3 4
8 7 6 5
GND OUTPUT CURRENT SENSE RT, CT
FEATURES
FEEDBACK GAIN
* Micro-miniature (D) package * Pulse-width modulator * Current limiting (cycle-by-cycle) * Sawtooth generator * Stabilized power supply * Double pulse protection * Internal temperature-compensated reference
ORDERING INFORMATION
DESCRIPTION 8-Pin Plastic Dual In-Line Package (DIP) 8-Pin Plastic Dual In-Line Package (DIP) 8-Pin Ceramic Dual In-Line Package (CERDIP) 8-Pin Small Outline (SO) Package
Figure 1. Pin Configuration
APPLICATIONS
* Switched-mode power supplies * DC motor controller inverter * DC/DC converter
TEMPERATURE RANGE 0 to +70C -55 to +125C -55 to +125C 0 to +70C
ORDER CODE NE5561N SE5561N SE5561FE NE5561D
DWG # SOT97-1 SOT97-1 0580A SOT96-1
BLOCK DIAGRAM
RT, CT 5 REF VOLTAGE SAWTOOTH GENERATOR VCC
+ ERROR AMP FEEDBACK 3 - PWM R GAIN 4
7 S LATCH
OUTPUT
0.5V
-
STABILIZED SUPPLY 1 8 GND
8.2V 2 VZ
CURRENT SENSE
6
+
VCC
SL00385
Figure 2. Block Diagram
1994 Aug 31
1
853-0889 13721
Philips Semiconductors
Product specification
Switched-mode power supply control circuit
NE/SE5561
ABSOLUTE MAXIMUM RATINGS
SYMBOL VCC Supply1 Voltage-forced mode Current-fed mode Output transistor (at 20-30V max) IOUT VOUT PD TA Output current Output voltage Output duty cycle Maximum total power dissipation Operating temperature range SE5561 NE5561 NOTES: 1. See Voltage-Current-fed supply characteristic curve. -55 to +125 0 to 70 C C 40 VCC+1.4V 98 0.75 mA V % W +18 30 V mA PARAMETER RATING UNIT
DC ELECTRICAL CHARACTERISTICS
VCC=12V, TA=25C, unless otherwise specified. SYMBOL PARAMETER TEST CONDITIONS SE5561 Min 3.69 3.65 7.8 8.2 100 200 Typ 3.75 Max 3.84 3.88 8.8 Min 3.57 3.55 7.8 8.2 100 200 NE5561 Typ 3.75 Max 3.96 3.98 8.8 UNIT
Reference section
VREF VZ Internal ref voltage Internal zener ref Temp. coefficient of VREF Temp. coefficient of VZ TA=25C Over temperature *IL=7mA V V V ppm/C ppm/C
Oscillator section
Frequency range Initial accuracy Duty cycle range Over temperature RT and CT constant fO=20kHz Pin 6=250mV TA=25C Over temp. Single pulse inhibit delay Inhibit delay time for 20% overdrive at IOUT=20mA IOUT=40mA Current limit trip level .400 0.88 0.7 .500 0 50 5 98 0 100k 50 5 98 100k Hz % % A A s s V
Current limiting
IIN Input current -2 -10 -20 1.10 0.8 .600 .400 0.88 0.7 .500 -2 -10 -20 1.10 0.8 .600
Error amplifier
Open-loop gain Feedback resistor BW VOH VOL IOUT VCE Small-signal bandwidth Output voltage swing Output voltage swing 6.2 0.7 10k 3 6.2 0.7 60 10k 3 60 dB MHz V V
Output stage
Output current Sat Over temperature IC=20mA, Over temp. 20 0.4 20 0.4 mA V
1994 Aug 31
2
Philips Semiconductors
Product specification
Switched-mode power supply control circuit
NE/SE5561
DC ELECTRICAL CHARACTERISTICS
VCC=12V, TA=25C, unless otherwise specified. SYMBOL PARAMETER TEST CONDITIONS SE5561 Min Typ Max 10.0 13.0 20.0 20.0 21.0 22.0 30.0 19.0 20.0 21.0 Min NE5561 Typ Max 10.0 13.0 24.0 30.0 UNIT
Supply voltage/current
ICC VCC Supply current Supply voltage IZ=0, voltage-forced TA=25C Over temp. mA V
ICC=10mA, current-fed ICC=30mA current
Low supply protection
Pin 1 threshold 8 9 10.5 8 9 10.5 V
1994 Aug 31
3
Philips Semiconductors
Product specification
Switched-mode power supply control circuit
NE/SE5561
TYPICAL PERFORMANCE CHARACTERISTICS
Error Amplifier Open-Loop Gain
60 50 PHASE ANGLE (DEG) 40 GAIN (dB) 30 20 10 0 1k 0 -30 -60 -90 -120 -150 -180 1k (%) 100 90 80 70 60 50 40 30 20 10 0 10k 100k 1M 10M 0 1 2 3 V4 FREQUENCY (Hz) FREQUENCY (Hz) 4 5 6
Error Amplifier Open-Loop Phase
Transfer Curve of Pulse-Width Modulator Duty Cycle vs Input Voltage
10k
100k
1M
10M
Power Derating Curve
TOTAL PWR DISSIPATION (WATTS) 1.25 PT = VCC ICC + (VCC - VZ) IZ + [V7 I7 x DUTY CYCLE] 1000 100 50 30 f (kHz) 0.75 20 10 5 NE 0.25 2 SE 0 25 125 100 AMBIENT TEMPERATURE (C) 50 70 150 1 2 2.5 3 3.5 3
Typical Frequency Plot vs RT and CT
R=5k R=10k R=20k R=40k 5 CT RT 2 NE5561
1.00
0.50
4
4.5
C (nF)
Maximum Duty Cycle vs Base Voltage on Q1
100 MAXIMUM DUTY CYCLE (%) 90 80 70 60 50 40 30 20 10 0 0 1 2 V1 3 4 5 C V1 MAX (%)
Start-Up Circuit
V4 VZ 2 NE5561 R1 Q1 R2 4
Slow-Start Voltage
t d max is a function of f R2 VZ ) V BEQ1 R1 ) R2 t = R'C
SL00386
Figure 3. Typical Performance Characteristics
1994 Aug 31
4
Philips Semiconductors
Product specification
Switched-mode power supply control circuit
NE/SE5561
NE5561 Voltage-Current-Fed Supply Characteristics
mA
initially going to the extreme maximum (>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.)
20
10
0 0 10 20 30
V
Current-Fed Dropping Resistor
APPLICATIONS
VS
5V, 0.5A Buck Regulator Operates from 15V
RVCC
1
VCC
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 MAX circuit is required, as evidenced by Q1. The MAX limit may be calculated by using the relationship: R2 (8.2V) + R1 ) R2
SL00387
GND 8
V R VCC +
* V S CC (10 20mA)
Vd MAX
NOTE: See DC Electrical Characteristics for Current Fed VCC Range.
Figure 4. NE5561 Voltage-Current-Fed Supply Characteristics
The maximum duty cycle is then determined from the pulse-width modulator transfer graph, with R1 and R2 being defined from the desired conditions.
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
1994 Aug 31
5

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