®
L4971
1.5A STEP DOWN SWITCHING REGULATOR
UP TO 1.5A 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 L4971 is a step down monolithic power
switching regulator delivering 1.5A at a voltage
between 3.3V and 50V (selected by a simple ex-
ternal divider). Realized in BCD mixed technol-
ogy, the device uses an internal power D-MOS
transistor (with a typical Rdson of 0.25Ω) to ob-
tain very high efficency and high switching speed.
TYPICAL APPLICATION CIRCUIT
Vi=8V to 55V
5
R
1
20K
3
C
1
220µF
63V
C
7
220nF
C
2
2.7nF
2
7
Minidip
SO16W
ORDERING NUMBERS:
L4971 (Minidip)
L4971D (SO16)
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.
8
L4971
4
1
6
L1
126µH
(77120)
D1
GI
SB360
C
8
330µF
V
O
=3.3V/1.5A
C
5
100nF
R
2
9.1K
C
4
22nF
C
6
100nF
D97IN748A
May 2000
1/12
STMICROELECTRONICS [ STMICROELECTRONICS ]
