AN937 Datasheet, PDF (1/29 Pages) STMicroelectronics – The L4971 is a 1.5 A monolithic dc-dc converter

AN937
Application Note
Designing with L4971, 1.5 A high efficiency DC-DC converter
Introduction
The L4971 is a 1.5 A monolithic dc-dc converter, step- down, operating at fix frequency
continuous mode. It is designed in BCD60 II technology, and it is available in two plastic
packages, DIP8 and SO16L.
One direct fixed output voltage at 3.3 V ±1% is available, adjustable for higher output voltage
values, till 40 V, by an external voltage divider.
The operating input supply voltage ranges from 8 V to 55 V, while the absolute value, with no
load, is 60V. New internal design solutions and superior technology performance allow to
generate a device with improved efficiency in all the operating conditions and with reduced
EMI due to an innovative internal driving circuit, and reduced external component counts.
While internal limiting current and thermal shutdown are today considered standard
protection functions, mandatory for a safe load supply, oscillator with voltage feed forward
improves line regulation and overall control loop.
Soft-start avoids output over voltage at turn-on, while, shorting this pin to ground, the device
is completely disabled, going into zero consumption state.
Figure 1. Demonstration board
May 2011
Doc ID 5655 Rev 15
1/29
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