AS2842/3/4/5

Current Mode Controller

Description

The AS2842 family of control ICs provide pin-for-pin replace-

ment of the industry standard UC3842 series of devices. The

devices are redesigned to provide significantly improved

tolerances in power supply manufacturing. The 2.5 V refer-

ence has been trimmed to 1.0% tolerance. The oscillator

discharge current is trimmed to provide guaranteed duty

cycle clamping rather than specified discharge current. The

circuit is more completely specified to guarantee all param-

eters impacting power supply manufacturing tolerances.

In addition, the oscillator and flip-flop sections have been

now doubles as a synchronization input that can be easily

driven from open collector/open drain logic outputs. This

sync input is a high impedance input and can easily be used

for externally clocked systems. The new flip-flop topology

allows the duty cycle on the AS2844/5 to be guaranteed

between 49 and 50%. The AS2843/5 requires less than

0.5 mA of start-up current over the full temperature range.

Features

trimmed to 1.0% and

temperature-compensated

from - 40 to 105

° C

for precision duty cycle clamp

duty cycle clamp

simplifies synchronization

and hysteresis provide

more predictable start-up

and shutdown

better AC noise immunity

with current sense pulled

below ground

8L SOIC (D)

8

1

COMP

V

REG

7

2

V

FB

V

CC

6

3

I

SENSE

OUT

5

4

R

GND

PDIP (N)

8

1

COMP

V

REG

7

2

V

FB

V

CC

6

3

I

SENSE

OUT

5

4

R

GND

Ordering Information

Description

Temperature Range

Order Codes

8-Pin Plastic DIP

-40 to 105

° C

AS2842/3/4/5N

8-Pin Plastic SOIC

-40 to 105

° C

AS2842/3/4/5D-8

ASTEC Semiconductor

37