AN938 Datasheet, PDF (1/33 Pages) STMicroelectronics – The L4973 family is a 3.5 A monolithic DC-DC converter

AN938
Application note
Designing with L4973, 3.5 A high efficiency
DC-DC converter
Introduction
The L4973 family is a 3.5 A monolithic DC-DC converter in step-down topology operating in
continuous mode. It uses BCD60 II technology and is available in two plastic packages,
power DIP18 (12+3+3) and SO20 (12+4+4).
Two versions of the device are available. The L4973V3.3 sets the output voltage without any
voltage divider at 3.3 V and the L4973V5.1 at 5.1 V.
Both the regulators can control higher output voltage values by using an external voltage
divider.
The operating input supply voltage ranges from 8 V to 55 V, while the absolute value with no
load is 60 V.
New internal design solutions and superior technological performance have allowed us to
develop and produce a device with improved efficiency in all operating conditions and with
fewer external components.
While internal current limiting and thermal shutdown are today considered standard
protection functions mandatory for a safe load supply, an oscillator with voltage feed-forward
improves line regulation and overall control loop. The soft-start function does not allow
output overvoltages at turn-on, and the synchronization function can reduce EMI problems
in multi-output power supplies. The inhibit function, introduced for power management in
equipment having standby features, when active (high), reduces device power consumption
by a few tens of µA.
A demonstration board for the L4973 is available through order code EVAL4973 (see
Figure 1).
Figure 1. EVAL4973 demonstration board
April 2009
Doc ID 5410 Rev 10
AM03483v1
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