NTE1721 & NTE1723
Integrated Circuit
Pulse Width Modulator (PWM) Regulator
Description:
The NTE1721 and NTE1723 are pulse width modulator controlcircuits designed to offer improved
performance and lowered external parts count when implemented for controlling all types of switching
power supplies. The nochip +5.1V reference is trimmed to
1% and the input commonmode range
of the errror amplifier includes the reference voltage, thus eliminating the need for external divider
resistors. A sync input to the oscillator enables multiple units to be slaved or a single unit to be syn-
chronized to an external system clock. A wide range of dead time can be programmed by a single
resistor connected between the C
T
and the Discharge pins. These devices also feature a builtin
softstart circuitry, requiring only an external timing capacitor. A shutdown pin controls both the soft
start circuitry and the output stages, provided instantaneous turnoff through the PWM latch with
pulsed shutdown, as well as softstart recycle with longer shutdown commands. The under voltage
lockout inhibits the outputs and the changing of the softstart capacitor when V
CC
is below nominal.
The output stages are totempole design capable of sinking and sourcing in excess of 200mA. The
output stages of the NTE1721 features NOR logic resulting in a low output for an off state while the
NTE1723 utilizes OR logic which gives a high output when off.
Features:
D
8V to 35V Operation
D
+5.1V
1% Trimmed Reference
D
100Hz to 400kHz Oscillator Range
D
Separate Oscillator Sync Pin
D
Adjustable Dead Time Control
D
Input Undervoltage Lockout
D
Latching PWM to Prevent Multiple Pulses
D
PulsebyPulse Shutdown
D
Dual Source/Sink Outputs:
400mA Peak
Absolute Maximum Ratings: (Note 1)
Supply Voltage, V
CC
+40V
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Collector Supply Voltage, V
C
+40V
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Logic Inputs
0.3V to +5.5V
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Analog Inputs
0.3V to V
CC
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Output Current, Source or Sink, I
O
500mA
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Reference Output Current, I
ref
50mA
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Oscillator Charging Current
5mA
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Power Dissipation (T
A
= +25
C), P
D
1000mW
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Derate Above 50
C
10mW/
C
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Power Dissipation (T
C
= +25
C), P
D
2000mW
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Derate Above 25
C
16mW/
C
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Operating Junction Temperature, T
J
+150
C
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Storage Temperature Range, T
stg
55
to +125
C
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Thermal Resistance, JunctiontoAmbient, R
thJA
100
C/W
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Thermal Resistance, JunctiontoCase, R
thJC
60
C/W
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Lead Temperature (During Soldering, 10sec), T
L
+300
C
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Note 1 Values beyond which damage may occur
Recommended Operating Conditions:
Parameter
Symbol
Min
Typ
Max
Unit
Supply Voltage
V
CC
8.0
35.0
V
Collector Supply Voltage
V
C
4.5
35.0
V
Output Sink/Source Current
Steady State
I
O
0
100
mA
Peak
0
400
mA
Reference Load Current
I
ref
0
20
mA
Oscillator Frequency Range
f
osc
0.1
400
kHz
Oscillator Timing Resistor
R
T
2.0
150
k
Oscillator Timing Capacitor
C
T
0.001
0.2
F
Deadtime Resistor Range
R
D
0.5
Operating Ambient Temperature Range
T
A
0
70
C
Electrical Characteristics: (V
CC
= +20V, T
A
= 0
to +70
C unless otherwise specified)
Parameter
Symbol
Test Conditions
Min
Typ
Max
Unit
Reference Section
Reference Output Voltage
V
ref
T
J
= +25
C
5.0
5.1
5.2
V
Line Regulation
Reg
line
+8V
V
CC
+35V
10
20
mV
Load Regulation
Reg
load
0mA
I
L
20mA
20
50
mV
Temperature Stability
V
ref
/
T
20
mV
Total Output Variation (Includes Line
and Load Regulation over
Temperature
V
ref
4.95
5.25
V
Short Circuit Current
I
SC
V
ref
= 0V, T
J
= +25
C
80
100
mA
Output Noise Voltage
V
n
10Hz
f
10kHz, T
J
= +25
C
40
200
V
rms
Long Term Stability
S
T
J
= +25
C, Note 2
20
50
mV/kHr
Oscillator Section (Tested at f
osc
= 40kHz, R
T
= 3.6k
, C
T
= 0.001
F, R
D
= 0
unless otherwise specified)
Initial Accuracy
T
J
= +25
C
2
6
%
Frequency Stability with Voltage
f
osc
/V
CC
+8V
V
CC
+35V
1
2
%
Frequency Stability with Temperature
f
osc
/T
3
%
Minimum Frequency
f
min
R
T
= 150k
, C
T
= 0.2
F
50
Hz
Maximum Frequency
f
max
R
T
= 2k
, C
T
= 1.0nF
400
kHz
Current Mirror
I
RT
= 2mA
1.7
2.0
2.2
mA
Clock Amplitude
3.0
3.5
V
Clock Width
T
J
= +25
C
0.3
0.5
1.0
s
Sync Threshold
1.2
2.0
2.8
V
Sync Input Current
Sync Voltage = +3.5V
1.0
2.5
mA
Error Amplifier Section (V
CM
= +5.1V)
Input Offset Voltage
V
IO
2.0
10.0
mV
Input Bias Current
I
IB
1.0
10.0
A
Note 2. Since long term stability cannot be measured on each device before shipment, this specifica-
tion is an engineering estimate of average stability from lot to lot.
Electrical Characteristics (Cont'd): (V
CC
= +20V, T
A
= 0
to +70
C unless otherwise specified)
Parameter
Symbol
Test Conditions
Min
Typ
Max
Unit
Error Amplifier Section (Cont'd) (V
CM
= +5.1V)
DC Open Loop Gain
A
VOL
R
L
10M
60
75
dB
Low Level Output Voltage
V
OL
0.2
0.5
V
High Level Output Voltage
V
OH
3.8
5.6
V
Common Mode Rejection Ratio
CMRR
+1.5V
V
CM
+5.2V
60
75
dB
Power Supply Rejection Ratio
PSRR
+8V
V
CC
+35V
50
60
dB
PWM Comparator Section
Minimum Duty Cycle
DC
min
0
%
Maximum Duty Cycle
DC
max
45
49
%
Input Threshold, Zero Duty Cycle
V
TH
f
osc
= 40kHz, R
T
= 3.6k
,
0.6
0.9
V
Input Threshold, Maximum Duty Cycle
C
T
= 0.01
F, R
D
= 0
3.3
3.6
V
Input Bias Current
I
IB
0.05
1.0
A
SoftStart Section
SoftStart Current
V
shutdown
= 0V
25
50
80
A
SoftStart Voltage
V
shutdown
= 2.0V
0.4
0.6
V
Shutdown Input Current
V
shutdown
= 2.5V
0.4
1.0
mA
Output Drivers (Each Output, V
CC
= +20V)
Output Low Level
V
OL
I
sink
= 20mA
0.2
0.4
V
I
sink
= 100mA
1.0
2.0
V
Output High Level
V
OH
I
sink
= 20mA
18
19
V
I
sink
= 100mA
17
18
V
Under Voltage Lockout
V
UL
V8 and V9 = High
6.0
7.0
8.0
V
Collector Leakage
I
C(leak)
V
C
= +35V, Note 3
200
A
Rise Time
t
r
C
L
= 1.0nF, T
J
= +25
C
100
600
ns
Fall Time
t
f
C
L
= 1.0nF, T
J
= +25
C
50
300
ns
Shutdown Delay
t
ds
V
DS
= +3V, C
S
= 0, T
J
= +25
C
0.2
0.5
s
Supply Current
I
CC
V
CC
= +35V
14
20
mA
Note 3.Applies to NTE1721 Only, due to polarity of output pulses.
Application Information (Shutdown Options):
Since both the compensation and softstart terminals (Pin9 and Pin8) have current source pullups,
either can readily accept a pulldown signal which only has to sink a maximum of 100
A to turn off
the outputs. This is subject to the added requirement of discharging whatever external capacitance
may be attached to these pins.
An alternate approach is the use of the shutdown circuitry of Pin10 which has been improved to en-
hance the available shutdown options. Activating this circuit by applying a positive signal on Pin10
performs two functions: the PWM latch is immediately set providing the fastest turnoff signal to the
outputs; and a 150
A current sink begins to discharge the external softstart capacitor. If the shut-
down command is short, the PWM signal is terminated without significant discharge of the softstart
capacitor, thus, allowing, for example, a convenient implementation of pulsebypulse current limit-
ing. Holding Pin10 high for a longer duration, however, will ultimately discharge this external capaci-
tor, recycling slow turnon upon release.
Pin10 should not be left floating as noise pickup could conceivably interrupt normal operation.
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