Datasheet NTE1721, NTE1723 Datasheet (NTE)

NTE1721 & NTE1723

Integrated Circuit

Pulse Width Modulator (PWM) Regulator

Description:

The NTE1721 and NTE1723 are pulse width modulator control–circuits designed to offer improved
performance and lowered external parts count when implemented for controlling all types of switching
power supplies. The no–chip +5.1V reference is trimmed to ±1% and the input common–mode 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 syn­chronized to an external system clock. A wide range of dead time can be programmed by a single
resistor connected between the CT and the Discharge pins. These devices also feature a built–in
soft–start circuitry, requiring only an external timing capacitor. A shutdown pin controls both the soft–
start circuitry and the output stages, provided instantaneous turn–off through the PWM latch with
pulsed shutdown, as well as soft–start recycle with longer shutdown commands. The under voltage
lockout inhibits the outputs and the changing of the soft–start capacitor when VCC is below nominal.
The output stages are totem–pole 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 Pulse–by–Pulse Shutdown
D Dual Source/Sink Outputs: ±400mA Peak

Absolute Maximum Ratings: (Note 1)

Supply Voltage, VCC +40V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Collector Supply Voltage, V

C

+40V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Logic Inputs –0.3V to +5.5V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Analog Inputs –0.3V to V
Output Current, Source or Sink, I
Reference Output Current, I

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

O

ref

±500mA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

50mA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Oscillator Charging Current 5mA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Power Dissipation (TA = +25°C), P

D

1000mW. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Derate Above 50°C 10mW/°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Power Dissipation (TC = +25°C), P

D

2000mW. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Derate Above 25°C 16mW/°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Operating Junction Temperature, T
Storage Temperature Range, T
Thermal Resistance, Junction–to–Ambient, R
Thermal Resistance, Junction–to–Case, R

J

stg

thJA

thJC

Lead Temperature (During Soldering, 10sec), T

–55° to +125°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

L

+150°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

100°C/W. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

60°C/W. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

+300°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Note 1 Values beyond which damage may occur

CC

Recommended Operating Conditions:

Parameter Symbol Min Typ Max Unit

Supply Voltage V
Collector Supply Voltage V
Output Sink/Source Current

Steady State

I

CC

C

O

8.0 – 35.0 V

4.5 – 35.0 V

0 – ±100 mA

Peak 0 – ±400 mA
Reference Load Current I
Oscillator Frequency Range f
Oscillator Timing Resistor R
Oscillator Timing Capacitor C
Deadtime Resistor Range R
Operating Ambient Temperature Range T

ref

osc

T

T
D
A

0 – 20 mA

0.1 – 400 kHz

2.0 – 150 kΩ

0.001 – 0.2 µF

0.5 – – Ω
0 – 70 °C

Electrical Characteristics: (VCC = +20V, TA = 0° to +70°C unless otherwise specified)

Parameter Symbol Test Conditions Min Typ Max Unit

Reference Section

Reference Output Voltage V
Line Regulation Reg
Load Regulation Reg
Temperature Stability ∆V
Total Output Variation (Includes Line

ref

∆V
and Load Regulation over
Temperature

TJ = +25°C 5.0 5.1 5.2 V

ref

+8V ≤ VCC ≤ +35V – 10 20 mV

line

0mA ≤ IL ≤ 20mA – 20 50 mV

load

/∆T – 20 – mV

ref

4.95 – 5.25 V

Short Circuit Current I
Output Noise Voltage V

SC

V

= 0V, TJ = +25°C – 80 100 mA

ref

10Hz ≤ f ≤ 10kHz, TJ = +25°C – 40 200 µV

n

rms

Long Term Stability S TJ = +25°C, Note 2 – 20 50 mV/kHr
Oscillator Section (Tested at f

= 40kHz, RT = 3.6kΩ, CT = 0.001µF, RD = 0Ω unless otherwise specified)

osc

Initial Accuracy TJ = +25°C – ±2 ±6 %
Frequency Stability with Voltage f

osc/VCC

Frequency Stability with Temperature f
Minimum Frequency f
Maximum Frequency f

osc

min
max

+8V ≤ VCC ≤ +35V – ±1 ±2 %

/T – ±3 – %

RT = 150kΩ, CT = 0.2µF – 50 – Hz

RT = 2kΩ, CT = 1.0nF 400 – – kHz
Current Mirror IRT = 2mA 1.7 2.0 2.2 mA
Clock Amplitude 3.0 3.5 – V
Clock Width TJ = +25°C 0.3 0.5 1.0 µs
Sync Threshold 1.2 2.0 2.8 V
Sync Input Current Sync Voltage = +3.5V – 1.0 2.5 mA
Error Amplifier Section (VCM = +5.1V)
Input Offset Voltage V
Input Bias Current I

IO

IB

– 2.0 10.0 mV
– 1.0 10.0 µA

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): (VCC = +20V, TA = 0° to +70°C unless otherwise specified)

Parameter Symbol Test Conditions Min Typ Max Unit

Error Amplifier Section (Cont’d) (VCM = +5.1V)

DC Open Loop Gain A
Low Level Output Voltage V
High Level Output Voltage V

VOL

OH

RL ≤ 10MΩ 60 75 – dB

OL

– 0.2 0.5 V

3.8 5.6 – V
Common Mode Rejection Ratio CMRR +1.5V≤ VCM ≤ +5.2V 60 75 – dB
Power Supply Rejection Ratio PSRR +8V ≤ VCC ≤ +35V 50 60 – dB

PWM Comparator Section

Minimum Duty Cycle DC
Maximum Duty Cycle DC
Input Threshold, Zero Duty Cycle

V
Input Threshold, Maximum Duty Cycle
Input Bias Current I

min

max

TH

IB

f

= 40kHz, RT = 3.6kΩ,

osc

CT = 0.01µF, RD = 0Ω

– – 0 %

45 49 – %

0.6 0.9 – V

– 3.3 3.6 V
– 0.05 1.0 µA

Soft–Start Section

Soft–Start Current V
Soft–Start Voltage V
Shutdown Input Current V

shutdown
shutdown
shutdown

= 0V 25 50 80 µA
= 2.0V – 0.4 0.6 V

= 2.5V – 0.4 1.0 mA
Output Drivers (Each Output, VCC = +20V)
Output Low Level V

Output High Level V

Under Voltage Lockout V
Collector Leakage I

C(leak)

Rise Time t
Fall Time t
Shutdown Delay t
Supply Current I

OH

ds

CC

I

OL

UL

= 20mA – 0.2 0.4 V

sink

I

= 100mA – 1.0 2.0 V

sink

I

= 20mA 18 19 – V

sink

I

= 100mA 17 18 – V

sink

V8 and V9 = High 6.0 7.0 8.0 V
VC = +35V, Note 3 – – 200 µA
CL = 1.0nF, TJ = +25°C – 100 600 ns

r

CL = 1.0nF, TJ = +25°C – 50 300 ns

f

VDS = +3V, CS = 0, TJ = +25°C – 0.2 0.5 µs
VCC = +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 soft–start terminals (Pin9 and Pin8) have current source pull–ups,
either can readily accept a pull–down signal which only has to sink a maximum of 100µA 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 en­hance 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 turn–off signal to the
outputs; and a 150µA current sink begins to discharge the external soft–start capacitor. If the shut­down command is short, the PWM signal is terminated without significant discharge of the soft–start
capacitor, thus, allowing, for example, a convenient implementation of pulse–by–pulse current limit­ing. Holding Pin10 high for a longer duration, however, will ultimately discharge this external capaci­tor, recycling slow turn–on upon release.

Pin10 should not be left floating as noise pickup could conceivably interrupt normal operation.

Pin Connection Diagram

Invert Input 1

Non–Invert Input

Sync

OSC Output

Discharge
Soft–Start

16 9

C
R

2
3

4
5

T

6

T

7
8

V

16

ref

V

15

IN

Output B

14

V

13

C

GND

12

Output A

11

Shutdown

10

Compensation

9

18

.870 (22.0) Max .260 (6.6)

Max

.200 (5.08)

Max

.100 (2.54)

.700 (17.78)

.099 (2.5) Min