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Pulse-Width-Modulation Control Circuits
FEATURES
Complete PWM Power Control Circuitry Uncommitted Outputs for 200 Ma Sink or Source Current Output Control Selects Single-Ended or Push-Pull Operation Internal Circuitry Prohibits Double Pulse at Either Output Variable Dead-Time Provides Control over Total Range Internal Regulator Provides a Stable 5-V Reference Supply,5% Circuit Architecture Allows Easy Synchronization
Error AMP 1 NONINV INPUT INV INPUT FEEDBACK DEAD-TIME CONTROL CT RT GND C1
TL494
SOP16/DIP16
(TOP VIEW)
1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 NONINV INPUT INV INPUT REF OUT OUTPUT CONTROL Vcc C2 E2 E1 Error AMP 2
DESCRIPTION
The TL494 incorporate on a single monolithic chip all the functions required in the construction of a pulse-width-modulation control, these devices offer the systems engineer the flexibility to tailor ORDERING INFORMATION Device Package the power supply control circuitry to his application. TL494D 16 SOP The TL494 contains an error amplifier, an on-chip adjustable TL494N 18 DIP oscillator, a dead-time control comparator, pulse-steering control flip-flop, a 5-volt, 5% precision regulator, and output-control circuit. The error amplifier exhibits a common-mode voltage range from -0.3 volts to Vcc -2 volts. The dead-time control comparator has a fixed offset that provides approximately 5% dead time when externally altered. The on-chip oscillator may be bypassed by terminating R T (pin 6) to the reference output and providing a sawtooth in put to CT (pin 5), or it may be used to drive the common circuits in synchronous multiple-rail power supplies. The uncommited output transistors provide either common-emitter or emitter-follower output capability. Each Device provides for push-pull or single-ended output operation, which may be selected through the output-control funct -ion. The architecture of these devices prohibits the possibility of either output being pulsed twice during push -pull operation.
Functional Block Diagram
RT CT
OUTPUT CONTROL
OSCILLATOR
Q1 C1 E1
DEAD TIME CONTROL
0.1V
DEAD-TIME CONTROL COMPARATOR C1
Q2 C2 E2
PWM COMPARATOR ERROR AMPLIFIER PULSE-STEERING FLIP-FLOP
NONINVERTING INPUT INVERTING INPUT
+ 1 -
Vcc
ERROR AMPLIFIER NONINVERTING INPUT INVERTING INPUT + 2 FEEDBACK
REFERENCE
Vref
GND
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Pulse-Width-Modulation Control Circuits
Parameter measurement information
TL494
Vcc = 15V
Vcc DEAD-TIME
150 2W C1 E1
150 2W OUTPUT 1 OUTPUT 2
TEST INPUTS
FEEDBACK 12K RT CT 0.01uF (+) (-) (+) (-) 50K OUTPUT CONTROL GND ERROR
C2 E2
REF OUT
TEST CIRCUIT
VOLTAGE AT C1
Vcc
0 Vcc
VOLTAGE AT C2
0
VOLTAGE AT C T
DEAD-TIME CONTROL INPUT 0V
THRESHOLD VOLTAGE
THRESHOLD VOLTAGE FEEDBACK
0.7 V DUTY CIRCLE 0% MAX
0%
Figure 1. OPERATIONAL TEST CIRCUIT AND WAVEFORMS
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Pulse-Width-Modulation Control Circuits
AMPLIFIER UNDER TEST
+ -
TL494
FEEDBACK TERMINAL
+
Vref
-
OTHER AMPLIFIER
FIGURE 2. AMPLIFIER CHARACTERISTICS 15 V (EACH OUTPUT CIRCUIT) 68 2W OUTPUT CL =15pF (Includes probe and jig capacitance)
t
f
t
r
90%
90%
10%
10%
TEST CIRCUIT
OUTPUT VOLTAGE WAVEFORM
FIGURE 3. COMMON-EMITTER CONFIGURATION
15 V (EACH OUTPUT CIRCUIT)
90%
90%
10% 68 2W CL =15pF (Includes probe and jig capacitance) TEST CIRCUIT t
r
10%
t
f
OUTPUT VOLTAGE WAVEFORM
FIGURE 4. EMITTER-FOLLOWER CONFIGURATION
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Pulse-Width-Modulation Control Circuits
ABSOLUTE MAXIMUM RATINGS OVER OPERATING FREE-AIR TEMPERATURE RANGE
Rating Supply voltage, Vcc Amplifier input voltage Collector output voltage Collector output current Operating free-air temperature range Storage temperature range Lead temperature 1,6 mm from case for 10 seconds Value 41 Vcc +0.3 41 250 0 to 70 -65 to 150 260
TL494
Unit V mA
o
C
RECOMMENDED OPERATING CONDITIONS
Parameter Supply voltage, Vcc Amplifier input voltage, Vi Collector output voltage, Vo Collector output current (each transistor) Current into feedback terminal Timing capacitor, C T Timing resistor, R T Oscillator frequency Operating free-air temperature, T A Value MIN 7 -0.3 MAX 40 Vcc -2 40 200 0.3 10000 500 300 70 Unit
V
mA nF K KHz
o
0.47 1.8 1 0
C
Electrical characteristics over recommended operatng free-air temperature range, Vcc=15V, f= 10 kHz(unless otherwise noted).
Parameter Output voltage (Vref) Input regulation Output regulation Output voltage change with temperature Short-circuit output current*** Test Conditions* lo = 1mA Vcc = 7V to 40 V Io = 1mA to 10mA TA = MIN to MAX Vref = 0 MIN 4.75 Value TYP** 5 2 1 0.2 35 MAX 5.25 25 15 1 Unit V mV % mA
Oscillator section (See Figure 1)
Parameter Frequency Standard deviation of frequency**** Frequency change with voltage Frequency change with temperature**** Test Conditions* CT=0.01F, R T=12K All values of Vcc, C T,RT, and TA constant Vcc=7V to 40V, T A=25oC CT=0.01F, R T=12K, TA = MIN to MAX MIN Value TYP** 10 10 0.1 1 % MAX Unit KHz
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HTC
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Pulse-Width-Modulation Control Circuits
Electrical characteristics over recommended operating free-air temperature range, Vcc=15V, f=10kHz (unless otherwise noted) Amplifier section (See Figure 2)
SYMBOL Input offset voltage Input offset current Input bias current Common-mode input voltage range Open-loop voltage amplification Unity-gain bandwidth Common-mode rejection ratio Output sink current (pin 3) Output source current (pin 3) TEST CONDITIONS Vo(pin 3)=2.5V Vo(pin 3)=2.5V Vo(pin 3)=2.5V MIN.
TL494
TYP**. MAX. UNIT 2 25 0.2 10 250 1 nA V dB kHz dB mA mA
Vcc = 7V to 40V -0.3~-2 Vo=3V, R L=2K, Vo=0.5~3.5V 70 95 Vo=0.5~3.5V, R L=2K 800 Vo= 40V, T A= 25oC VID=-15mV~-5V, V( pin3)=0.7V VID=15mV~5V, V( pin3)=3.5V 65 0.3 -2 80 0.7
*For conditions shown as MIN or MAX, use the appropriate value specified under recommended operating conditions. ** All typical values except for parameter changes with temperature are at TA =25 oC *** Duration of the short-circuit should not exceed one second. **** Standard deviation is a measure of the statistical distribution about the mean as derived from the formula. ***** Temperature coefficient of timing capacitor and timing resistor not taken into account.
Output section
PARAMETER Collector off-state current Emitter off-state current
Collector-emitter saturation voltage
Common-emitter Emitter-follower Output control input current
TEST CONDITIONS VCE=40V, Vcc=40V VCC=VC=40V,V E=0 VE=0, IC=200mA Vc=15V, I E=-200mA VI=Vref
MIN.
TYP* 2 1.1 1.5
MAX. UNIT 100 -100 1.3 V 2.5 3.5 mA
Dead-time control-section (See Figure 1)
PARAMETER Input bias current(pin4) Maximum duty cycle, each output Input threshold voltage(pin 4) TEST CONDITIONS VI=0 to 5.25V =0, CT=0.1uF, R T=12K VI (pin 4) Zero duty cycle Maximum duty cycle MIN. TYP* -2 45 3 0 MAX. UNIT -10 % 3.3 V
PMW comparator section (See Figure 1)
PARAMETER Input threshold voltage (pin3) Input sink current (pin 3) TEST CONDITIONS Zero duty cycle V(pin3) = 0.7V MIN. 0.3 TYP* 4 0.7 MAX. UNIT 4.5 V mA
Total device
PARAMETER Standby supply current Average supply current TEST CONDITIONS Pin 6 at Vref, all other inputs and outputs open VI(pin 4)= 2V MIN. VCC=15V VCC=40V TYP* 6 9 7.5 MAX. UNIT 10 mA 15
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Switching characteristics, T
PARAMETER Output voltage rise time Output voltage fall time Output voltage rise time Output voltage fall time
A
TL494
MIN. TYP* 100 25 100 40 MAX. UNIT 200 100 200 100
= 25 oC
TEST CONDITIONS Common-emitter configuration Emitter-follower configuration
ns
* All typical values except for temperature coefficient are at T A = 25oC
t osc - R T
500 OPEN-LOOP VOLTAGE GAIN VOL (dB) A 100 90 OSCILLATOR FREQUENCYosc (Hz) t 100 80 70 60 50 40 30 20 10 0 1.0 k 5.0 k 20 k 50 k 200 500 1.0 1.1 10 100 1.0k 10k 100k TIMING RESISTANCE() TR FREQUENCY f(Hz)
Vcc=15V VO=3.0V RL=2.0
0 EXCESS PHASE (DEGREES) 20 40 60 80 100 120 140 160 180 1.0M
10 k
1.0 k
500
VCE(sat) -
I
C
VCE 1.9
I
E
SATURATION VOLTAGE CE (sat) (V) V
SATURATION VOLTAGE CE (sat) (V) V 100 200 300
2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6
1.8 1.7 1.6 1.5 1.4 1.3 1.2 1.1 0 100 200 300
0.4 0
10 9.0 SUPPLY CURRENT Icc (mA) 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.0 0 0 5.0
COLLECTOR CURRENT Ic ( ) ICC - V CC
EMITTER CURRENT IE (mA)
10
15
20
25
30
35
40
SUPPLY VOLTAGE Vcc (V)
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