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NTE1753
Integrated Circuit
Pulse Width Modulator (PWM) Control Circuit
Description:
The NTE1753 is a fixed–frequency pulse width modulation control circuit in a 14–Lead DIP type package incorporating the primary building blocks required for the control of a switching power supply.
An internal–linear sawtooth oscillator frequency is determined by:
^
f
OSC
R
D C
T
T
Output pulse width modulation is accomplished by comparison of the positive sawtooth waveform
1.1
across capacitor C
to either of two control signals. The output is enabled only during that portion
T
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.
The control signals are external inputs that can be fed into the dead–time control, the error amplifier
inputs, or the feed–back input. The dead–time control comparator has an effective 120mV input of fset
which limits the minimum output dead time to approximately the first 4% of the sawtooth–cycle time.
This would result in a maximum duty cycle of 96%. Additional dead time may be imposed on the output by setting the dead time–control input to a fixed voltage, ranging between 0 to 3.3V.
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 dead time control input, down to
zero, as the voltage at the feedback pin varies from 0.5 to 3.5V. Both error amplifiers have a common–
mode input range from –0.3V to (V
–2V), and may be used to sense power supply output voltage
CC
and current. The error–amplifier outputs are active high and are 0 red together at the non–inverting
input of the pulse–width modulator comparator. With this configuration, the amplifier that demands
minimum output on time, dominates control of the loop.
The NTE1753 has an internal 5.0V reference capable of sourcing up to 10mA of load currents for external bias circuits. The reference has an internal accuracy of ±5% with a typical thermal drift of less
than 50mV over an operating temperature range of 0 to +70°C.
Features:
D Complete Pulse Width Modulation Control Circuitry
D On–Chip Oscillator with Master or Slave Operation
D On–Chip Error Amplifiers
D On–Chip 5.0 Volt Reference
D Adjustable Dead Time Control
D Uncommitted Output Transistor for 200mA Source or Sink
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Absolute Maximum Ratings: (TA = 0° to +70°C unless otherwise specified)
Power Supply Voltage, V
Collector Output Voltage, V
Collector Output Current, I
Amplifier Input Voltage, V
Power Dissipation (T
A
Operating Junction Temperature, T
Operating Ambient Temperature Range, T
Storage Temperature Range, T
Thermal Resistance, Junction to Ambient, R
Power Derating Factor, 1/R
Derating Ambient Temperature, T
42V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CC
42V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
C
250mA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
C
V
in
≤ 45°C), PD 1000mW. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
+125°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
J
0° to +70°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
A
–55° to +125°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
stg
+80°C/W. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Θ
JA
12.5mW/°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Θ
JA
+45°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
A
Recommended Operating Conditions:
Parameter Symbol Min Typ Max Unit
CC
+0.3V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Power Supply Voltage V
Collector Output Voltage V
Collector Output Current I
Amplifier Input Voltage V
Current Into Feedback Terminal I
Reference Output Current I
Timing Resistor R
Timing Capacitor C
Oscillator Frequency f
OSC
CC
C
C
in
f b
ref
T
T
7.0 15 40 V
– 30 40 V
– – 200 mA
–0.3 – VCC–2 V
– – 0.3 mA
– – 10 mA
1.8 47 500 kΩ
0.0047 0.001 10 µF
1.0 25 200 kHz
Electrical Characteristics: (VCC = 15V, CT = 0.01µF, RT = 12kΩ. For typical values TA = +25°C,
for min/max values T
Parameter Symbol Test Conditions Min Typ Max Unit
Reference Section
Reference Voltage V
Line Regulation Reg
Load Regulation Reg
Short–Circuit Output Current I
Output Section
ref
lineVCC
loadIO
SC
IO = 1mA 4.75 5.0 5.25 V
= 7V to 40V – 2 25 mV
= 1mA to 10mA – 3 15 mV
V
= 0 15 35 75 mA
ref
is 0° to +70°C unless otherwise specified.)
A
Collector Off–State Current I
Emitter Off–State Current I
Collector–Emitter Saturation Voltage V
Output Voltage Rise Time t
Output Voltage Fall Time t
C(off)
E(off)
V
VCE = 40V, VCC = 40V – 2 100 µA
VCC = VC = 40V, VE = 0 – – –100 µA
sat(C)IC
sat(E)IE
TA = +25°C, Common Emitter – 100 200 ns
r
TA = +25°C, Emitter Follower – 100 200 ns
TA = +25°C, Common Emitter – 25 100 ns
f
TA = +25°C, Emitter Follower – 40 100 ns
= 200mA, VE = 0, Common Emitter – 1.1 1.3 V
= 200mA, VC = 15V, Emitter Follower – 1.5 2.5 V
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Electrical Characteristics (Cont’d): (VCC = 15V, CT = 0.01µF, RT = 12kΩ. For typical values
T
= +25°C, for min/max values TA is 0° to +70°C unless other-
A
wise specified.)
Parameter Symbol Test Conditions Min Typ Max Unit
Error Amplifier Section
Input Offset Voltage V
Input Offset Current I
Input Bias Current I
Common Mode Input
Voltage Range
Low
High V
Open–Loop Voltage Gain A
Unity Gain Crossover Frequency f
V
IO
IO
IB
ICR
VOL
c
Phase Margin at Unity Gain Φm VO = 0.5V to 3.5V, RL = 2kΩ – 65 – deg.
Common Mode Rejection Ratio CMRR VCC = 40V 65 90 – dB
Power Supply Rejection Ratio PSRR ∆VCC = 33V, VO = 2.5V, RL = 2kΩ – 100 – dB
Output Sink Current IO– V
Output Source Current IO+ V
PWM Comparator Section
Input Threshold Voltage V
TH
Input Sink Current II– V
Dead–Time Control Section
Input Bias Current (Pin4) I
Maximum Output Duty Cycle DC
Input Threshold Voltage (Pin4) V
IB(DT)
max
TH
Oscillator Section
Frequency f
Standard Deviation of Frequency αf
Frequency Change with ∆f
OSC
OSC
OSC
Temperature
Frequency Change with Voltage ∆f
OSC
Total Device
Standby Supply Current I
Average Supply Current I
CC
S
V
V
V
VCC = 40V, TA = +25°C
= 2.5V – 2 10 mV
O(Pin3)
= 2.5V – 5 250 nA
C(Pin3)
= 2.5V – –0.1 –1.0 µA
O(Pin3)
–0.3 – – V
–2
CC
– – V
∆VO = 3V, VO = 0.5V to 3.5V, RL = 2kΩ 70 95 – dB
VO = 0.5V to 3.5V, RL = 2kΩ – 350 – kHz
= 0.7V 0.3 0.7 – mA
O(Pin3)
= 3.5V –2 –4 – mA
O(Pin3)
Zero Duty Cycle – 3.5 4.5 V
= 0.7V 0.3 0.7 – mA
(Pin3)
VIN = 0 to 5.25V – –2 –10 µA
VIN = 0, CT = 0.01µF, RT = 12kΩ 90 96 100 %
VIN = 0, CT = 0.001µF, RT = 47k–Ω – 92 100 %
Zero Duty Cycle – 2.8 3.3 V
Maximum Duty Cycle 0 – – V
CT = 0.001µF, RT = 47kΩ – 25 – kHz
CT = 0.001µF, RT = 47kΩ – 3 – %
0° ≤ ∆TA ≤ +70°C – – 12 %
(∆T)
CT = 0.01µF, RT = 12kΩ – – 12 %
(∆V) VCC = 7V to 40V, TA = +25°C – 1 – %
VCC = 15V, all other inputs and outputs
– 5.5 10 mA
open
VCC = 40V, all other inputs and outputs
– 7.0 15 mA
open
V
= 2V, CT = 0.001µF, RT = 47kΩ – 7 – mA
(Pin4)
Note 1. Standard deviation is a measure of the statistical distribution about the mean as derived from
the formula:
α =
N
S
n = 1
(X
n
– X)
2
N – 1
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Pin Connection Diagram
Non–Inverting Input (1)
Inverting Input (1)
Feedback/
PWM Comparator Input
Dead–Time Control
1
2
3
4
C
5
T
R
6
T
7GND
14 8
14
Non–Inverting Input (2)
13
Inverting Input (2)
V
12
ref
11
N.C.
V
10
CC
9 Collector
8 Emitter
17
.785 (19.95) Max
.300 (7.62)
.200
(5.08)
Max
.100 (2.45) .099 (2.5) Min
.600 (15.24)
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