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Semiconductor
S494
Pulse Width Modulation
Description
The S494 is a monolithic integrated circuit which includes all the necessary building blocks for the design of pulse width modulate(PWM) switching power supplies, including push-pull, bridge and series configuration. The device can operate at switching frequencies between 1KHz and 300KHz and output voltage up to 40V. The S494 is specified over an operating temperature range of -40to85.
Features
* Uncommitted output transistors capable of 200mA source or sink * Internal protection from double pulsing of out-puts with narrow pulse widths or with supply voltages bellows specified limits * Easily synchronized to other circuits * Dead time control comparator * Output control selects single-ended or push-pull operation
Ordering Information
Type NO. S494 Marking S494 Package Code SOP-16
Outline Dimensions
unit : mm
PIN Connections 1. Non-INV Input 2. INV Input 3. Feed-Back 4. Dead-Time Control 5. CT 6. RT
7. GND 8. C1 9. E1 10. E2 11. C2 12. Vcc 13 Output Control 14. Ref Out 15. INV-Input 16. Non-INV Input
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S494
Absolute Maximum Ratings
Characteristic
supply voltage Voltage From Any Pin to Ground (except pin 8 and pin 11) Output Collector Voltage Peak Collector Current Power Dissipation Operating Temperature Storage Temperature
Ta=25C
Symbol
VCC VIN VC1, VC2 IC1, IC2 PD Topr Tstg
Ratings
42 VCC+0.3 42 250 1500 -40 ~ 85 -65 ~ 150
Unit
V V V mA mW C C
Recommended Operating Condition
Characteristic
supply voltage Voltage on Any Pin Except Pin 8 and 11(Referenced to Ground) Output Voltage Output Collector Current Timing Capacitor Timing Capacitor Timing Resistor Oscillator Frequency
Symbol
VCC VIN VC1, VC2 IC1, IC2 Ct Ct Rt fOSC
Min.
7 -0.3 -0.3 470 1.8 1
Max.
40 VCC+0.3 40 200 10 500 300
Unit
V V V mA PF KHz
Electrical Characteristics Reference Section
Characteristic
Reference Voltage Line Regulation Load Regulation Temperature Coefficient
Symbol
Vref VLINE VLOAD -
Test Condition
Iref = 1.0mA 7V < Vcc < 40V
Min. Typ. Max.
4.75 5.00 2 1 0.01 5.25 25 15 0.03
Unit
V mV mV %/C
1mA< IREF <10mA
0C < Ta <70C
Oscillator Section
Characteristic
Oscillator Frequency Oscillator Frequency Change Over Operating Temperature Range
Symbol
fOSC fSOC
Test Condition
Ct=0.01 , Rt=12 Ct=0.01 , Rt=12
Min. Typ. Max.
10 2
Unit
%
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S494
Dead Time Control Section
Characteristic
Input Bias Current (Pin4) Max. Duty cycle, Each Output Input Threshold Voltage Zero Duty Max Duty
Symbol
IIB(DT) DC(Max) VTH
Test Condition
Vcc = 15V, 0V < V4 < 5.25V Vcc = 15V, Pin4 = 0V, Output Control Pin = Vref -
Min. Typ. Max.
43 0 -2 3 -10 45 3.3 -
Unit
%
V
Error Amplifier Section
Characteristic
Input Offset Voltage Input Offset Current Input Bias Current Input Common Mode voltage Range Large Signal Open Loop Voltage Range Unity Gain Band width
Symbol
VIOS IIOS IIB VICR GVO fC
Test Condition
V3 = 2.5V V3 = 2.5V V3 = 2.5V 7V VCC 40V 0.5V V3 3.5V -
Min. Typ. Max.
-0.3 60 2 25 0.2 74 650 10 250 1 VCC -
Unit
mV
nA
V dB
PWM Comparator Section (Pin3)
Characteristic
Inhibit Threshold Voltage Output Source Current Output Sink Current
Symbol
VTHI Io
+
Test Condition
Zero duty cycle 0.5V < V3 < 3.5V 0.5V< V3 < 3.5V
Min. Typ. Max.
2 -0.2 4 -0.6 4.5 -
Unit
V
mA mA
Io-
Output Section
Characteristic
Output Saturation Voltage Common-Emitter Emitter-Follower
Symbol
VCE(SAT) IC(off) IE(off)
Test Condition
VE= 15V, IC = 200mA VC =15V, IE = 200mA VCC = VC = 40V, VE = 0 VCC = VC = 40V, VE = 0
Min. Typ. Max.
1.1 1.5 2 1.3 2.5 100 -100
Unit
V
Collector off-state Current Emitter off-state Current
Output Control(Pin 13)
Output Control Voltage Required for single-Ended or Parallel Output Operation Output Control Voltage Required for Push-pull operation VOCL VOCH 2.4 0.4 -
V V
Total Device
Standby power Supply Current ICC 6 10
mA
: These limits apply when the voltage measured at Pin 3 is with in the range specified.
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S494
Output AC Characteristic
Characteristic
Rise Time Common Emitter Emitter Follower Common Emitter Emitter Follower
Symbol
tr tf -
Test Condition
Min. Typ. Max.
100 100 25 40 200 200 100 100
Unit
ns
Fall Time
-
-
Block Diagram
V cc Ref Out G ND RT CT 12 14 7 6 Os c 5 De a d T i me CO MP A R A T O R De a d-T i me Con t r ol Non -i n v In pu t In v -In pu t Non -i n v In pu t In v -In pu t Fe e d-Ba c k 4 + + PWM CO MP A R A T O R EA 2 + T F.F R e fe r e n c e R e gu l a t or 8 9 C1 E1 13 O u t pu t Con t r ol
11 C 2 10 E2
1 2 16 15 3 + -
EA 1
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S494
INFORMATION
The basic oscillator(switching)frequency is controlled by an external resistor (Rt) and capacitor(Ct). The relationship between the values of Rt Ct and frequency is shown in. The level of the sawtooth wave form is compared with an error voltage by the pulse width modulated comparator. The output of the PWM Comparator directs the pulse steering flip flop and the output control logic. The error voltage is generated by the error amplifier. The error amplifier boosts the voltage difference between the output and the 5V internal reference. See Figure7 for error amp sensing techniques. The second error amp is typically used to implement current limiting. The output control logic (Pin13) selects either push-pull or single-ended operation of the output transistors (see Figure6). The dead time control prevents on-state overlap of the output transistors as can be seen is Figure5. The dead time is approximately 3 to 5% of the total period if the dead time control(pin4) is grounded. This dead time can be increased by connecting the dead time control to a voltage up to 5 V. The frequency response of the error amps can be modified by using external resistors and capacitors. These components are typically connected between the compensation terminal (pin3) and the inverting input of the error amps(pin2 or pin15). The switching frequency of two or more S494 circuits can be synchronized. The timing capacitor, Ct is connected as shown in Figure8. Charging current is provided by the master circuit. Discharging is through all the circuits slaved to the master. Rt is required only for the master circuit.
Operating Waveform
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S494
Test Circuit
Fig.1Error Amplifier Test Circuit
+ VIN 2
Fig.2 Current Limit sense Amplifier Test Circuit
1+
ERROR
1+
ERROR
-
AMP
V3
V REF + V IN 15 2
-
AMP
V3
16 +
ERROR
16 +
ERROR
VREF
15
AMP
-
AMP
Fig. 3 Common-Emitter Configuration Test circuit and Waveform
15V DC 68 C Ea c h o u t p u t Trans is tor E 15p F Vc
Fig. 5 Dead-Time and Feedback Control Test Circuit
Vcc=15V 150 12 2W 4 DEAD 8 Vcc TEST C1 TIME 9 Inputs 3 FEED BACK E1 12K 6 RT 5 CT 11 C2 10 1 (+) 0.01uF 2 E2 (-) 16 (+) 15 (-) 13 OUTPUT REF 14 CONTROL OUT 50K 7 GND 150 2W OUTPUT1
OUTPUT2
90% 10% Tr Tf
90% 10%
Fig. 4 Emitter-Follower Configuration Test circuit and waveform Voltage waveform
15V DC C Each output Trans is tor 68 VE 15pF GND 90% 10% Tr Tf 90% 10%
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S494
APPLICATION CIRCUIT
Fig. 6 Output Connections for Single-Ended and Push-Pull Configurations
Q1 8 OUTPUT CONTROL 9 C1 E1 1 TO 500 m A(MAX) V REF R2 QC
Fig. 7 Error Amplifier Sensing Techniques
TO OUTPUT VOLTAGE OF SYSTEM R1 1(16) + Vo 2(15) ERROR AMP
Q2 11 C2 0 < VOC < 4V 10 E2
3
QE
SINGLE-ENDED CONFIGURATION
POSITIVE OUTPUT VOLTAGE
VREF Q1 8 2. 4VPUSH-PULL CONFIGURATION
Fig. 8 Slaving Tow or More Control Circuits
Fig. 9Error Amplifier and Current Limit Sense Amplifier Output Circuits
V cc V REF
14 V REF 6 5 RT MASTER CT 14 V REF 6 RT 5 CT SLAV E (ADDITIONAL CIRCUITS)
RT
CT
TO REMAINDER OF ERROR AMPLIFIER CIRCUIT
TO REMAINDER OF ERROR AMPLIFIER CIRCUIT
0.6m A
TO COMPENSATION PWM COMPARATOR INPUT
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S494
Electrical Characteristic Curves
Fig. 1 VCE(sat) -IC Fig. 2 VCE -IE
Fig. 3 tOSC - RT
Fig. 4 AVOL , Phase - f
Fig. 5 ICC - VCC
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S494
These AUK products are intended for usage in general electronic equipments(Office and communication equipment, measuring equipment, domestic electrification, etc.). Please make sure that you consult with us before you use these AUK products in equipments which require high quality and/or reliability, and in equipments which could have major impact to the welfare of human life(atomic energy control, airplane, spaceship, traffic signal, combustion central, all types of safety device, etc.). AUK cannot accept liability to any damage which may occur in case these AUK products were used in the mentioned equipments without prior consultation with AUK.
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