Device Operating
Temperature Range Package

SEMICONDUCTOR
TECHNICAL DATA
SWITCHMODE
PULSE WIDTH MODULATION
CONTROL CIRCUIT
ORDERING INFORMATION
TL494CN
TL494IN
TA = 0° to +70°C
TA = – 25° to +85°C
Plastic
Plastic
PIN CONNECTIONS
Order this document by TL494/D
N SUFFIX
PLASTIC PACKAGE
CASE 648
CT
RT
Ground
C1
1
Inv
Input
C2
Q2 E2
E1
1
0.1 V
Oscillator
VCC5.0 V
REF
(Top View)
Noninv
Input
Inv
Input
Vref
Output
Control
VCC
Noninv
Input
Compen/PWN
Comp Input
Deadtime
Control
Error
Amp
+
2
3
4
5
6
7
89
10
11
12
13
14
15
16
2Error
Amp
+
Q1
D SUFFIX
PLASTIC PACKAGE
CASE 751B
(SO–16)
TL494CD SO–16
1
MOTOROLA ANALOG IC DEVICE DATA

 
  
The TL494 is a fixed frequency, pulse width modulation control circuit
designed primarily for SWITCHMODE power supply control.
Complete Pulse Width Modulation Control Circuitry
On–Chip Oscillator with Master or Slave Operation
On–Chip Error Amplifiers
On–Chip 5.0 V Reference
Adjustable Deadtime Control
Uncommitted Output Transistors Rated to 500 mA Source or Sink
Output Control for Push–Pull or Single–Ended Operation
Undervoltage Lockout
MAXIMUM RATINGS (Full operating ambient temperature range applies,
unless otherwise noted.)
Rating Symbol TL494C TL494I Unit
Power Supply Voltage VCC 42 V
Collector Output Voltage VC1,
VC2 42 V
Collector Output Current
(Each transistor) (Note 1) IC1, IC2 500 mA
Amplifier Input Voltage Range VIR –0.3 to +42 V
Power Dissipation @ TA 45°C PD1000 mW
Thermal Resistance,
Junction–to–Ambient RθJA 80 °C/W
Operating Junction Temperature TJ125 °C
Storage Temperature Range Tstg –55 to +125 °C
Operating Ambient Temperature Range
TL494C
TL494I
TA0 to +70
25 to +85
°C
Derating Ambient Temperature TA45 °C
NOTE: 1.Maximum thermal limits must be observed.
Motorola, Inc. 1996 Rev 1
TL494
2MOTOROLA ANALOG IC DEVICE DATA
RECOMMENDED OPERATING CONDITIONS
Characteristics Symbol Min Typ Max Unit
Power Supply Voltage VCC 7.0 15 40 V
Collector Output Voltage VC1, VC2 30 40 V
Collector Output Current (Each transistor) IC1, IC2 200 mA
Amplified Input Voltage Vin –0.3 VCC – 2.0 V
Current Into Feedback Terminal lfb 0.3 mA
Reference Output Current lref 10 mA
T iming Resistor RT1.8 30 500 k
T iming Capacitor CT0.0047 0.001 10 µF
Oscillator Frequency fosc 1.0 40 200 kHz
ELECTRICAL CHARACTERISTICS (VCC = 15 V, CT = 0.01 µF, RT = 12 k, unless otherwise noted.)
For typical values TA = 25°C, for min/max values TA is the operating ambient temperature range that applies, unless otherwise noted.
Characteristics Symbol Min Typ Max Unit
REFERENCE SECTION
Reference Voltage (IO = 1.0 mA) V ref 4.75 5.0 5.25 V
Line Regulation (VCC = 7.0 V to 40 V) Regline 2.0 25 mV
Load Regulation (IO = 1.0 mA to 10 mA) Regload 3.0 15 mV
Short Circuit Output Current (V ref = 0 V) ISC 15 35 75 mA
OUTPUT SECTION
Collector Off–State Current
(VCC = 40 V, VCE = 40 V) IC(off) 2.0 100 µA
Emitter Off–State Current
VCC = 40 V, VC = 40 V, VE = 0 V) IE(off) –100 µA
Collector–Emitter Saturation V oltage (Note 2)
Common–Emitter (VE = 0 V, IC = 200 mA)
Emitter–Follower (VC = 15 V, IE = –200 mA) Vsat(C)
Vsat(E)
1.1
1.5 1.3
2.5
V
Output Control Pin Current
Low State (VOC 0.4 V)
High State (VOC = Vref)IOCL
IOCH
10
0.2
3.5 µA
mA
Output Voltage Rise Time
Common–Emitter (See Figure 12)
Emitter–Follower (See Figure 13)
tr
100
100 200
200
ns
Output Voltage Fall Time
Common–Emitter (See Figure 12)
Emitter–Follower (See Figure 13)
tf
25
40 100
100
ns
NOTE: 2. Low duty cycle pulse techniques are used during test to maintain junction temperature as close to ambient temperature as possible.
TL494
3
MOTOROLA ANALOG IC DEVICE DATA
ELECTRICAL CHARACTERISTICS (VCC = 15 V, CT = 0.01 µF, RT = 12 k, unless otherwise noted.)
For typical values TA = 25°C, for min/max values TA is the operating ambient temperature range that applies, unless otherwise noted.
Characteristics Symbol Min Typ Max Unit
ERROR AMPLIFIER SECTION
Input Offset Voltage (VO (Pin 3) = 2.5 V) VIO 2.0 10 mV
Input Offset Current (VO (Pin 3) = 2.5 V) IIO 5.0 250 nA
Input Bias Current (VO (Pin 3) = 2.5 V) IIB –0.1 –1.0 µA
Input Common Mode Voltage Range (VCC = 40 V, TA = 25°C) VICR –0.3 to VCC–2.0 V
Open Loop Voltage Gain (VO = 3.0 V, VO = 0.5 V to 3.5 V, RL = 2.0 kΩ) AVOL 70 95 dB
Unity–Gain Crossover Frequency (VO = 0.5 V to 3.5 V, RL = 2.0 k) fC– 350 kHz
Phase Margin at Unity–Gain (VO = 0.5 V to 3.5 V, RL = 2.0 k)φm65 deg.
Common Mode Rejection Ratio (VCC = 40 V) CMRR 65 90 dB
Power Supply Rejection Ratio (VCC = 33 V, VO = 2.5 V, RL = 2.0 k)PSRR 100 dB
Output Sink Current (VO (Pin 3) = 0.7 V) IO– 0.3 0.7 mA
Output Source Current (VO (Pin 3) = 3.5 V) IO+ 2.0 –4.0 mA
PWM COMPARATOR SECTION (Test Circuit Figure 11)
Input Threshold Voltage (Zero Duty Cycle) VTH 2.5 4.5 V
Input Sink Current (V(Pin 3) = 0.7 V) II– 0.3 0.7 mA
DEADTIME CONTROL SECTION (Test Circuit Figure 11)
Input Bias Current (Pin 4) (VPin 4 = 0 V to 5.25 V) IIB (DT) –2.0 –10 µA
Maximum Duty Cycle, Each Output, Push–Pull Mode
(VPin 4 = 0 V, CT = 0.01 µF, RT = 12 k)
(VPin 4 = 0 V, CT = 0.001 µF, RT = 30 k)
DCmax 45
48
45 50
50
%
Input Threshold Voltage (Pin 4)
(Zero Duty Cycle)
(Maximum Duty Cycle)
Vth
02.8
3.3
V
OSCILLATOR SECTION
Frequency (CT = 0.001 µF, RT = 30 k) fosc 40 kHz
Standard Deviation of Frequency* (CT = 0.001 µF, RT = 30 k)σfosc 3.0 %
Frequency Change with Voltage (VCC = 7.0 V to 40 V, T A = 25°C) fosc (V) 0.1 %
Frequency Change with Temperature (TA = Tlow to Thigh)
(CT = 0.01 µF, RT = 12 k)fosc (T) 12 %
UNDERVOLTAGE LOCKOUT SECTION
T urn–On Threshold (VCC increasing, Iref = 1.0 mA) Vth 5.5 6.43 7.0 V
TOTAL DEVICE
Standby Supply Current (Pin 6 at V ref, All other inputs and outputs open)
(VCC = 15 V)
(VCC = 40 V)
ICC
5.5
7.0 10
15
mA
Average Supply Current
(CT = 0.01 µF, RT = 12 k, V(Pin 4) = 2.0 V)
(VCC = 15 V) (See Figure 12) 7.0 mA
* Standard deviation is a measure of the statistical distribution about the mean as derived from the formula, σ
N
n = 1
Σ (Xn – X)2
N – 1
TL494
4MOTOROLA ANALOG IC DEVICE DATA
Figure 1. Representative Block Diagram
Figure 2. Timing Diagram
6
RTCT5
4
Deadtime
Control
Oscillator
0.12V
0.7V
0.7mA
+1
+
+
+
2
DQ
Ck
+
+
3.5V
4.9V
13
Reference
Regulator
Q1
Q2
8
9
11
10
12
VCC
VCC
12 3 1516 14 7
Error Amp
1Feedback PWM
Comparator Input Ref.
Output
Gnd
UV
Lockout
Flip–
Flop
Output Control
Error Amp
2
Deadtime
Comparator
PWM
Comparator
Q
Capacitor CT
Feedback/PWM Comp.
Deadtime Control
Flip–Flop
Clock Input
Flip–Flop
Q
Flip–Flop
Q
Output Q1
Emitter
Output Q2
Emitter
Output
Control
This device contains 46 active transistors.
TL494
5
MOTOROLA ANALOG IC DEVICE DATA
APPLICATIONS INFORMATION
Description
The TL494 is a fixed–frequency pulse width modulation
control circuit, incorporating the primary building blocks
required for the control of a switching power supply. (See
Figure 1.) An internal–linear sawtooth oscillator is frequency–
programmable by two external components, R T and CT. The
approximate oscillator frequency is determined by:
fosc 1.1
RT CT
For more information refer to Figure 3.
Output pulse width modulation is accomplished by
comparison of the positive sawtooth waveform across
capacitor CT to either of two control signals. The NOR gates,
which drive output transistors Q1 and Q2, are enabled only
when the flip–flop clock–input line is in its low state. This
happens only during that portion of time when the sawtooth
voltage is greater than the control signals. Therefore, an
increase in control–signal amplitude causes a corresponding
linear decrease of output pulse width. (Refer to the Timing
Diagram shown in Figure 2.)
The control signals are external inputs that can be fed into
the deadtime control, the error amplifier inputs, or the
feedback input. The deadtime control comparator has an
effective 120 mV input of fset which limits the minimum output
deadtime to approximately the first 4% of the sawtooth–cycle
time. This would result in a maximum duty cycle on a given
output of 96% with the output control grounded, and 48% with
it connected to the reference line. Additional deadtime may
be imposed on the output by setting the deadtime–control
input to a fixed voltage, ranging between 0 V to 3.3 V.
Functional Table
Input/Output
Controls Output Function fout
fosc =
Grounded Single–ended PWM @ Q1 and Q2 1.0
@ Vref Push–pull Operation 0.5
The pulse width modulator comparator provides a means
for the error amplifiers to adjust the output pulse width from
the maximum percent on–time, established by the deadtime
control input, down to zero, as the voltage at the feedback pin
varies from 0.5 V to 3.5 V. Both error amplifiers have a
common mode input range from –0.3 V to (VCC – 2V), and
may be used to sense power–supply output voltage and
current. The error–amplifier outputs are active high and are
ORed together at the noninverting input of the pulse–width
modulator comparator. With this configuration, the amplifier
that demands minimum output on time, dominates control of
the loop.
When capacitor CT is discharged, a positive pulse is
generated on the output of the deadtime comparator, which
clocks the pulse–steering flip–flop and inhibits the output
transistors, Q1 and Q2. With the output–control connected to
the reference line, the pulse–steering flip–flop directs the
modulated pulses to each of the two output transistors
alternately for push–pull operation. The output frequency is
equal to half that of the oscillator. Output drive can also be
taken from Q1 or Q2, when single–ended operation with a
maximum on–time of less than 50% is required. This is
desirable when the output transformer has a ringback
winding with a catch diode used for snubbing. When higher
output–drive currents are required for single–ended
operation, Q1 and Q2 may be connected in parallel, and the
output–mode pin must be tied to ground to disable the
flip–flop. The output frequency will now be equal to that of the
oscillator.
The TL494 has an internal 5.0 V reference capable of
sourcing up to 10 mA of load current for external bias circuits.
The reference has an internal accuracy of ±5.0% with a
typical thermal drift of less than 50 mV over an operating
temperature range of 0° to 70°C.
Figure 3. Oscillator Frequency versus
Timing Resistance
500 k
100 k
10 k
1.0 k
500
1.0 k 2.0 k 5.0 k 10 k 20 k 50 k 100 k 200 k 500 k 1.0 M
RT, TIMING RESISTANCE (
)
, OSCILLATOR FREQUENCY (Hz)f osc
VCC = 15 V
0.01
µ
F
0.1
µ
F
CT = 0.001
µ
F
TL494
6MOTOROLA ANALOG IC DEVICE DATA
Figure 4. Open Loop Voltage Gain and
Phase versus Frequency Figure 5. Percent Deadtime versus
Oscillator Frequency
Figure 6. Percent Duty Cycle versus
Deadtime Control Voltage
1.0 10 100 1.0 k 10 k 100 k 1.0 M
, OPEN LOOP VOLT AGE GAIN (dB)
VOL
f, FREQUENCY (Hz)
AVOL
0
20
40
60
80
100
120
140
160
180
, EXCESS PHASE (DEGREES)
φ
φ
VCC = 15 V
VO = 3.0 V
RL = 2.0 k
A
Figure 7. Emitter–Follower Configuration
Output Saturation Voltage versus
Emitter Current
500 k 1.0 k 10 k 100 k 500 k
fosc, OSCILLATOR FREQUENCY (Hz)
% DT, PERCENT DEADTIME (EACH OUTPUT)
CT = 0.001
µ
F
0.001
µ
F
0 1.0 2.0 3.0 3.5
VDT, DEADTIME CONTROL VOLTAGE (IV)
% DC, PERCENT DUTY CYCLE (EACH OUTPUT)
VCC = 15 V
VOC = Vref
1. CT = 0.01
µ
F
2. RT = 10 k
2. CT = 0.001
µ
F
2. RT = 30 k
2
1
Figure 8. Common–Emitter Configuration
Output Saturation Voltage versus
Collector Current
0 100 200 300 400
IE, EMITTER CURRENT (mA)
, SATURATION VOLTAGE (V)
CE(sat)
V
0 100 200 300 400
IC, COLLECTOR CURRENT (mA)
CE(sat)
, SATURATION VOLTAGE (V)V
Figure 9. Standby Supply Current
versus Supply Voltage
0 5.0 10 15 20 25 30 35 40
CC, SUPPLY CURRENT (mA)
VCC, SUPPLY VOLTAGE (V)
I
120
110
100
90
80
70
60
50
40
30
20
10
0
20
18
16
14
12
10
8.0
6.0
4.0
2.0
0
50
40
30
20
10
0
1.9
1.8
1.7
1.6
1.5
1.4
1.3
1.2
1.1
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
10
9.0
8.0
7.0
6.0
5.0
4.0
3.0
2.0
1.0
0
TL494
7
MOTOROLA ANALOG IC DEVICE DATA
Figure 10. Error–Amplifier Characteristics Figure 11. Deadtime and Feedback Control Circuit
Figure 12. Common–Emitter Configuration
Test Circuit and Waveform
+
+
Vin
Error Amplifier
Under Test
Feedback
Terminal
(Pin 3)
Other Error
Amplifier
Vref
VCC = 15V 150
2W
Output 1
Output 2
C1
E1
C2
E2
Ref
Out
Gnd
Output
Control
(+)
(+)
(–)
(–)
Feedback
Deadtime
Error
VCC
Test
Inputs
50k
RT
CT
150
2W
Figure 13. Emitter–Follower Configuration
Test Circuit and Waveform
RL
68 VC
CL
15pF
C
E
Q
Each
Output
Transistor
15V
90%
VCC
10%
90%
10%
trtf
RL
68
VEE
CL
15pF
C
E
Q
Each
Output
Transistor
15V
90% VEE
10%
90%
10%
trtf
Gnd
TL494
8MOTOROLA ANALOG IC DEVICE DATA
Figure 14. Error–Amplifier Sensing Techniques
Figure 15. Deadtime Control Circuit Figure 16. Soft–Start Circuit
Figure 17. Output Connections for Single–Ended and Push–Pull Configurations
VOTo Output
Voltage of
System
R1
1
2
Vref
R2
+Error
Amp
Positive Output Voltage
VO = Vref 1 + R1
3
+1
2
Vref
R2
VO
R1
Negative Output Voltage
To Output
Voltage of
System
Error
Amp
VO = Vref R1
R1
R2
Output
Control
Output Q
RTCT
DT
Vref 4
5
6
0.001
30k
R1
R2
Max. % on Time, each output
45 – 80
1 +
Output Q
Vref 4
DT
CS
RS
Output
Control Single–Ended
Q1
Q2
QC
1.0 mA to
500 mA
QE
2.4 V
VOC
V ref
Push–Pull
Q1
Q2
C1
E1
C2
E2
1.0 mA to 250 mA
1.0 mA to 250 mA
Output
Control
0
VOC
0.4 V
C1
E1
C2
E2
R2
R2
Figure 18. Slaving Two or More Control Circuits Figure 19. Operation with Vin > 40 V Using
External Zener
Figure 20. Pulse Width Modulated Push–Pull Converter
RTCT
6
5
Vref
RT
CTMaster
Vref
Slave
(Additional
Circuits)
RT
CT
5
6
Vin > 40V
RS
VZ = 39V
1N975A
VCC
5.0V
Ref
12
270 Gnd
7
+Vin = 8.0V to 20V
1
2
3
15
16
+
+
Comp
OC VREF DT CTRTGnd E1E2
13144567910
1M
33k
0.01 0.01
VCC
C1
C2
8
11
47
47
10
+
10k
4.7k4.7k 15k
Tip
32
+
T11N4934
L1
1N4934
240
+50
35V
4.7k
1.0
22
k
+
+VO = 28 V
IO = 0.2 A
12
L1 – 3.5 mH @ 0.3 A
T1 – Primary: 20T C.T. #28 A WG
T1 – Secondary: 12OT C.T. #36 AWG
T1 – Core: Ferroxcube 1408P–L00–3CB
All capacitors in
µ
F
TL494
0.001
50
35V
50
25V
Tip
32
TL494
9
MOTOROLA ANALOG IC DEVICE DATA
Test Conditions Results
Line Regulation V in = 10 V to 40 V 14 mV 0.28%
Load Regulation V in = 28 V, IO = 1.0 mA to 1.0 A 3.0 mV 0.06%
Output Ripple Vin = 28 V, IO = 1.0 A 65 mV pp P.A.R.D.
Short Circuit Current Vin = 28 V, RL = 0.1 1.6 A
Efficiency Vin = 28 V, IO = 1.0 A 71%
TL494
10 MOTOROLA ANALOG IC DEVICE DATA
Figure 21. Pulse Width Modulated Step–Down Converter
+Vin = 10V to 40V Tip 32A 1.0mH @ 2A +VO = 5.0 V
IO = 1.0 A
50
10V
+
5.1k MR850
0.1
150
5.1k 5.1k
47k
1.0M
0.1
3
2
1
14
15
16
Comp
+
Vref
+
VCC C1C2
50
50V
0.001
564137910
C
T
R
T
D.T. O.C. Gnd E1E2
+
47k
+
500
10V
150
47
11
12 8
TL494
Test Conditions Results
Line Regulation Vin = 8.0 V to 40 V 3.0 mV 0.01%
Load Regulation Vin = 12.6 V, IO = 0.2 mA to 200 mA 5.0 mV 0.02%
Output Ripple Vin = 12.6 V, IO = 200 mA 40 mV pp P.A.R.D.
Short Circuit Current Vin = 12.6 V, RL = 0.1 250 mA
Efficiency Vin = 12.6 V, IO = 200 mA 72%
TL494
11
MOTOROLA ANALOG IC DEVICE DATA
OUTLINE DIMENSIONS
N SUFFIX
PLASTIC PACKAGE
CASE 648–08
ISSUE R
NOTES:
1. DIMENSIONING AND TOLERANCING PER ANSI
Y14.5M, 1982.
2. CONTROLLING DIMENSION: INCH.
3. DIMENSION L TO CENTER OF LEADS WHEN
FORMED PARALLEL.
4. DIMENSION B DOES NOT INCLUDE MOLD FLASH.
5. ROUNDED CORNERS OPTIONAL.
–A–
B
FC
S
HGD
J
L
M
16 PL
SEATING
18
916
K
PLANE
–T–
M
A
M
0.25 (0.010) T
DIM MIN MAX MIN MAX
MILLIMETERSINCHES
A0.740 0.770 18.80 19.55
B0.250 0.270 6.35 6.85
C0.145 0.175 3.69 4.44
D0.015 0.021 0.39 0.53
F0.040 0.70 1.02 1.77
G0.100 BSC 2.54 BSC
H0.050 BSC 1.27 BSC
J0.008 0.015 0.21 0.38
K0.110 0.130 2.80 3.30
L0.295 0.305 7.50 7.74
M0 10 0 10
S0.020 0.040 0.51 1.01
____
D SUFFIX
PLASTIC PACKAGE
CASE 751B–05
(SO–16)
ISSUE J
NOTES:
1. DIMENSIONING AND TOLERANCING PER
ANSI Y14.5M, 1982.
2. CONTROLLING DIMENSION: MILLIMETER.
3. DIMENSIONS A AND B DO NOT INCLUDE
MOLD PROTRUSION.
4. MAXIMUM MOLD PROTRUSION 0.15 (0.006)
PER SIDE.
5. DIMENSION D DOES NOT INCLUDE DAMBAR
PROTRUSION. ALLOWABLE DAMBAR
PROTRUSION SHALL BE 0.127 (0.005) TOTAL
IN EXCESS OF THE D DIMENSION AT
MAXIMUM MATERIAL CONDITION.
18
16 9
SEATING
PLANE
F
J
M
RX 45
_
G
8 PLP
–B–
–A–
M
0.25 (0.010) B S
–T–
D
K
C
16 PL
S
B
M
0.25 (0.010) A S
T
DIM MIN MAX MIN MAX
INCHESMILLIMETERS
A9.80 10.00 0.386 0.393
B3.80 4.00 0.150 0.157
C1.35 1.75 0.054 0.068
D0.35 0.49 0.014 0.019
F0.40 1.25 0.016 0.049
G1.27 BSC 0.050 BSC
J0.19 0.25 0.008 0.009
K0.10 0.25 0.004 0.009
M0 7 0 7
P5.80 6.20 0.229 0.244
R0.25 0.50 0.010 0.019
____
TL494
12 MOTOROLA ANALOG IC DEVICE DATA
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TL494/D
*TL494/D*