© 2000 IMP, Inc.

408-432-9100/www.impweb.com

1

IMP38C/HC/42/3/4/5

IMP38C/HC/42/3/4/5

Key Features

N 384x Series Pinout with BiCMOS Technology

N Zero Cross-Conduction Current by Design

N 1MHz Operation

N 65ns Maximum Current-Sense Delay

N 120µA Maximum Start-Up Current

N 1.5mA Maximum Operating Current

N High Output Current Drive

– 1.0A, IMP38HC4x

– 0.5A, IMP38C4x

N 20V Maximum Supply Voltage

N 2.5V, 1%, Trimmed Error Amplifier Reference

N Trimmed Oscillator Discharge Current

N Pin-for-Pin Enhanced Replacements for Micrel

MIC38C/HC4x and GMT38C4x/HC4x

Block Diagrams

BiCMOS Cur

ent-Mode

PWM Contr

–

ation

–

ent

–

The IMP38C4x and IMP38HC4x are fixed frequency, high performance,

current-mode PWM controllers that are pin compatible with bipolar 384x

devices but feature improvements resulting from IMP’s BiCMOS

processing and circuit design. Notable among the improvements are zero

cross-conduction/shoot-through current, reduced start-up and operating

current, lower current-sense delay, higher frequency operation, full

supply voltage swing at the output and a 1% trimmed voltage reference.

IMP38C4x and IMP38HC4x output driver stage has zero cross-conduction

current. A proprietary output state-machine monitors each output

MOSFET and guarantees by design zero cross-conduction current. This is

an industry first for 384x PWM devices.

Under-voltage lockout (UVL) performance has been improved. When

the power supply voltage is below the startup voltage, internal circuitry

puts the output into a low impedance state. The output will sink 20mA

and remain below 1.3V, well below the turn-on threshold voltage of the

not rise above approximately 1.3V because the output UVLO circuit is

+

–

EA

OUT

6 (10)

RTCT

4 (7)

COMP

1 (1)

5V

Reference

7 (12)

8 (14)

FB

2 (3)

(11)

–

+

+

–

UVLO

+

–

COMP

PGND

(8)

Oscillator

TQ

S

Q

R

1V

R

2R

2.5V

Ref

(

) Pins Are 14-Pin Devices Only

38C/HC_01.eps

+

–

GND 5

AGND (9)

3 (5)

ISNS

Connection Notes

IMP38C4X, IMP38HC4X (8-Pin Devices)

50% Maximum Duty Cycle:

IMP38C44, IMP38HC44, IMP38C45, IMP38HC45

96% Maximum Duty Cycle:

IMP38C42, IMP38HC42, IMP38C43, IMP38HC43