L4978 Datasheet, PDF (1/12 Pages) STMicroelectronics – 2A STEP DOWN SWITCHING REGULATOR

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L4978
2A STEP DOWN SWITCHING REGULATOR
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 0.25Ω) to obtain very
high efficency and high switching speed.
TYPICAL APPLICATION CIRCUIT
Minidip
SO16W
ORDERING NUMBERS: L4978 (Minidip)
L4978D (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.
Vi=8V to 55V
C₁
220µF
63V
C₇
220nF
R₁
20K
C₂
2.7nF
5
8
L4978
3
4
2
7
16
L1
126µH
(77120)
V_O=3.3V/2A
C₅
100nF
R₂
9.1K
C₄
22nF
C₆
100nF
D1
GI
SB560
C₈
330µF
D98IN837A
May 2000
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