NTE NTE1753

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:
1.1
fOSC ^
RT D CT
Output pulse width modulation is accomplished by comparison of the positive sawtooth waveform
across capacitor CT to either of two control signals. The output is enabled 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.
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 offset
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 (VCC –2V), and may be used to sense power supply output voltage
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
Absolute Maximum Ratings: (TA = 0° to +70°C unless otherwise specified)
Power Supply Voltage, VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42V
Collector Output Voltage, VC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42V
Collector Output Current, IC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250mA
Amplifier Input Voltage, Vin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VCC +0.3V
Power Dissipation (TA ≤ 45°C), PD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1000mW
Operating Junction Temperature, TJ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +125°C
Operating Ambient Temperature Range, TA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0° to +70°C
Storage Temperature Range, Tstg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –55° to +125°C
Thermal Resistance, Junction to Ambient, RΘJA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +80°C/W
Power Derating Factor, 1/RΘJA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.5mW/°C
Derating Ambient Temperature, TA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +45°C
Recommended Operating Conditions:
Parameter
Symbol
Min
Typ
Max
Unit
Power Supply Voltage
VCC
7.0
15
40
V
Collector Output Voltage
VC
–
30
40
V
Collector Output Current
IC
–
–
200
mA
Amplifier Input Voltage
Vin
–0.3
–
VCC–2
V
Current Into Feedback Terminal
If b
–
–
0.3
mA
Reference Output Current
Iref
–
–
10
mA
Timing Resistor
RT
1.8
47
500
kΩ
Timing Capacitor
CT
0.0047
0.001
10
µF
fOSC
1.0
25
200
kHz
Oscillator Frequency
Electrical Characteristics: (VCC = 15V, CT = 0.01µF, RT = 12kΩ. For typical values TA = +25°C,
for min/max values TA is 0° to +70°C unless otherwise specified.)
Parameter
Symbol
Test Conditions
Min
Typ
Max
Unit
4.75
5.0
5.25
V
Reference Section
Reference Voltage
Vref
IO = 1mA
Line Regulation
Regline
VCC = 7V to 40V
–
2
25
mV
Load Regulation
Regload
IO = 1mA to 10mA
–
3
15
mV
Vref = 0
15
35
75
mA
Short–Circuit Output Current
ISC
Output Section
Collector Off–State Current
IC(off)
VCE = 40V, VCC = 40V
–
2
100
µA
Emitter Off–State Current
IE(off)
VCC = VC = 40V, VE = 0
–
–
–100
µA
Vsat(C)
IC = 200mA, VE = 0, Common Emitter
–
1.1
1.3
V
Vsat(E)
IE = 200mA, VC = 15V, Emitter Follower
–
1.5
2.5
V
TA = +25°C, Common Emitter
–
100
200
ns
TA = +25°C, Emitter Follower
–
100
200
ns
TA = +25°C, Common Emitter
–
25
100
ns
TA = +25°C, Emitter Follower
–
40
100
ns
Collector–Emitter Saturation Voltage
Output Voltage Rise Time
Output Voltage Fall Time
tr
tf
Electrical Characteristics (Cont’d): (VCC = 15V, CT = 0.01µF, RT = 12kΩ. For typical values
TA = +25°C, for min/max values TA is 0° to +70°C unless otherwise specified.)
Parameter
Symbol
Test Conditions
Min
Typ
Max
Unit
Error Amplifier Section
Input Offset Voltage
VIO
VO(Pin3) = 2.5V
–
2
10
mV
Input Offset Current
IIO
VC(Pin3) = 2.5V
–
5
250
nA
Input Bias Current
IIB
VO(Pin3) = 2.5V
–
–0.1
–1.0
µA
–0.3
–
–
V
VCC–2
–
–
V
∆VO = 3V, VO = 0.5V to 3.5V, RL = 2kΩ
70
95
–
dB
fc
VO = 0.5V to 3.5V, RL = 2kΩ
–
350
–
kHz
Φm
VO = 0.5V to 3.5V, RL = 2kΩ
–
65
–
deg.
Common Mode Input
Voltage Range
Low
VICR
VCC = 40V, TA = +25°C
High
Open–Loop Voltage Gain
Unity Gain Crossover Frequency
Phase Margin at Unity Gain
AVOL
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–
VO(Pin3) = 0.7V
0.3
0.7
–
mA
Output Source Current
IO+
VO(Pin3) = 3.5V
–2
–4
–
mA
VTH
Zero Duty Cycle
–
3.5
4.5
V
0.3
0.7
–
mA
PWM Comparator Section
Input Threshold Voltage
Input Sink Current
II–
V(Pin3) = 0.7V
Dead–Time Control Section
Input Bias Current (Pin4)
IIB(DT)
VIN = 0 to 5.25V
–
–2
–10
µA
Maximum Output Duty Cycle
DCmax
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
fOSC
CT = 0.001µF, RT = 47kΩ
–
25
–
kHz
αfOSC
CT = 0.001µF, RT = 47kΩ
–
3
–
%
–
–
12
%
–
–
12
%
–
1
–
%
VCC = 15V, all other inputs and outputs
open
–
5.5
10
mA
VCC = 40V, all other inputs and outputs
open
–
7.0
15
mA
V(Pin4) = 2V, CT = 0.001µF, RT = 47kΩ
–
7
–
mA
Input Threshold Voltage (Pin4)
VTH
Oscillator Section
Frequency
Standard Deviation of Frequency
Frequency Change with
Temperature
∆fOSC(∆T) 0° ≤ ∆TA ≤ +70°C
Frequency Change with Voltage
∆fOSC(∆V) VCC = 7V to 40V, TA = +25°C
CT = 0.01µF, RT = 12kΩ
Total Device
Standby Supply Current
Average Supply Current
ICC
IS
Note 1. Standard deviation is a measure of the statistical distribution about the mean as derived from
the formula:
α=
N
2
S (Xn – X)
n=1
N–1
Pin Connection Diagram
Non–Inverting Input (1)
1
14 Non–Inverting Input (2)
Inverting Input (1)
2
13 Inverting Input (2)
Feedback/
PWM Comparator Input
3
12 Vref
Dead–Time Control
4
11 N.C.
CT 5
10 VCC
RT 6
9
Collector
8
Emitter
GND
7
14
8
1
7
.300 (7.62)
.785 (19.95) Max
.200
(5.08)
Max
.100 (2.45)
.600 (15.24)
.099 (2.5) Min