AN1061 Datasheet, PDF (1/21 Pages) STMicroelectronics – 2A HIGH EFFICIENCY DC-DC CONVERTERY

AN1061
APPLICATION NOTE
DESIGNING WITH L4978,
2A HIGH EFFICIENCY DC-DC CONVERTERY
1 INTRODUCTION
The L4978 is a 2A monolithic dc-dc converter, step- down , operating at fix frequency contin-
uous mode.
It is realised in BCD60 II technology, and it’s available in two plastic packages, MINIDIP and
SO16L.
One direct fixed output voltage at 3.3V ±1% is available, adjustable for higher output voltage
values, till 40V, by an external voltage divider.
The operating input supply voltage ranges from 8V to 55V, 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 inno-
vative 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 feedforward improves line
regulation and overall control loop.
Soft-start avoids output overvoltages at turn-on, while, shorting this pin to ground, the device
is completely disabled, going into zero consumption state.
Figure 1.
AN1061/0505
Rev. 9
1/21