L4971
1.5A STEP DOWN SWITCHING REGULATOR
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FEATURES
UP TO 1.5A STEP DOWN CONVERTER
OPERATING INPUT VOLTAGE FROM 8V TO
55V
PRECISE 3.3V (±1%) INTERNAL
REFERENCE VOLTAGE
OUTPUT VOLTAGE ADJUSTABLE FROM
3.3V TO 50V
SWITCHING FREQUENCY ADJUSTABLE UP
TO 300KHz
VOLTAGE FEEDFORWARD
ZERO LOAD CURRENT OPERATION
INTERNAL CURRENT LIMITING (PULSE-
BYPULSE AND HICCUP MODE)
INHIBIT FOR ZERO CURRENT
CONSUMPTION
PROTECTION AGAINST FEEDBACK
DISCONNECTION
THERMAL SHUTDOWN
SOFT START FUNCTION
Figure 1. Package
DIP8
SO16W
Table 1. Order Codes
Part Number
L4971
L4971D
L4971D013TR
Package
DIP8
SO16W
SO16 in Tape & Reel
A switching frequency up to 300KHz is achievable
(the maximum power dissipation of the packages
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 feed-
back loop disconnection, inhibit for zero current
consumption and thermal shutdown.
The device is available in plastic dual in line, DIP8
for standard assembly, and SO16W for SMD as-
sembly.
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DESCRIPTION
The L4971 is a step down monolithic power
switching regulator delivering 1.5A at a voltage be-
tween 3.3V and 50V (selected by a simple external
divider). Realized in BCD mixed technology, the
device uses an internal power D-MOS transistor
(with a typical Rdson of 0.25Ω) to obtain very high
efficency and high switching speed.
Figure 1. Block Diagram
Vi=8V to 55V
5
R
1
20K
3
C
1
220µF
63V
C
7
220nF
C
2
2.7nF
2
7
8
L4971
4
1
6
L1
126µH
(77120)
D1
STPS
3L60U
C
8
330µF
V
O
=3.3V/1.5A
C
5
100nF
R
2
9.1K
C
4
22nF
C
6
100nF
D97IN748A
May 2005
Rev. 11
1/13
STMICROELECTRONICS [ STMICROELECTRONICS ]
