L4973
3.5A step down switching regulator
Features
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Up to 3.5A step down converter
Operating input voltage from 8V to 55V
3.3V and 5.1V (±1%) fixed output, and
adjustable outputs from:
– 0.5V to 50V (3.3 type)
– 5.1V to 50V (5.1 type)
Frequency adjustable up to 300kHz
Voltage feed forward
Zero load current operation (min 1mA)
Internal current limiting (pulse by pulse and
HICCUP mode)
Precise 5.1V (1.5%) reference voltage
externally available
Input/output synchronization function
Inhibit for zero current consumption (100mA
typ. at V
CC
= 24V)
Protection against feedback disconnection
Thermal shutdown
Output over voltage protection
Soft start function
DIP-18 (12+3+3)
SO-20 (12+4+4)
Description
The L4973 is a step down monolithic power
switching regulator delivering 3.5A at fixed
voltages of 3.3V or 5.1V and using a simple
external divider output adjustable voltage up to
50V. Realized in BCD mixed technology, the
device uses an internal power D-MOS transistor
(with a typical R
DS(on)
of 0.15Ω) to obtain very
high efficiency and very fast switching times.
Switching frequency up to 300KHz are 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 40V
cover the majority of the today applications.
Features of this new generation of DC-DC
converter includes pulse by pulse current limit,
hiccup mode for output short circuit protection,
voltage feed forward regulation, soft start,
input/output synchronization, protection against
feedback loop disconnection, inhibit for zero
current consumption and thermal shutdown.
Packages available are in plastic dual in line, DIP-
18 (12+3+3) for standard assembly, and SO20
(12+4+4) for SMD assembly.
8
12
9
1
4,5,6,10
13,14,15
C
BOOT
V
O
(3.3V or 5.1V)
L1
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Figure 1.
Internal schematic diagram
V
CC
(8V to 55V)
R
OSC
7
L4973
16
17
11
C
IN
C2
3
2
R
COMP
C
OSC
C
SS
C
COMP
D1
C
OUT
D97IN554A
May 2007
Rev 17
1/27
27
STMICROELECTRONICS [ STMICROELECTRONICS ]
