UP TO 2A STEP DOWN CONVERTER

OPERATING INPUT VOLTAGE FROM 8V TO

55V

PRECISE 3.3V (

±1%) INTERNAL REFER-

ENCE VOLTAGE

OUTPUT VOLTAGE ADJUSTABLE FROM

3.3V TO 50V

SWITCHING FREQUENCY ADJUSTABLE UP

TO 500KHz

VOLTAGE FEEDFORWARD

ZERO LOAD CURRENT OPERATION

INTERNAL CURRENT LIMITING (PULSE-BY-

PULSE AND HICCUP MODE)

INHIBIT FOR ZERO CURRENT CONSUMP-

TION

PROTECTION AGAINST FEEDBACK DIS-

CONNECTION

THERMAL SHUTDOWN

SOFT START FUNCTION

DESCRIPTION

The L4978 is a step down monolithic power

switching regulator delivering 2A at a voltage be-

tween 3.3V and 50V (selected by a simple exter-

nal divider). Realized in BCD mixed technology,

the device uses an internal power D-MOS transis-

tor (with a typical Rdson of 0.25

Ω) to obtain very

high efficency and high switching speed.

A switching frequency up to 500KHz is achiev-

able (the maximum power dissipation of the pack-

ages must be observed).

A wide input voltage range between 8V to 55V

and output voltages regulated from 3.3V to 50V

cover the majority of today’s applications.

Features of this new generations of DC-DC con-

verter include pulse-by-pulse current limit, hiccup

mode for short circuit protection, voltage feedfor-

ward regulation, soft-start, protection against

feedback loop disconnection, inhibit for zero cur-

rent consumption and thermal shutdown.

The device is available in plastic dual in line,

MINIDIP 8 for standard assembly, and SO16W

for SMD assembly.

May 2000

®

ORDERING NUMBERS: L4978 (Minidip)

L4978D (SO16)

L4978

2A STEP DOWN SWITCHING REGULATOR

Minidip

SO16W

D98IN837A

5

2

8

4

1

L4978

220

µF

63V

330

µF

Vi=8V to 55V

20K

2.7nF

9.1K

22nF

3

7

L1

126

µH

(77120)

6

D1

GI

SB560

100nF

220nF

100nF

TYPICAL APPLICATION CIRCUIT

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