SM8172A Datasheet, PDF (7/17 Pages) Nippon Precision Circuits Inc – 2-output Power Supply IC

SM8172A
12. FUNCTIONAL DESCRIPTION
12-1. Series Regulator
12-1-1. Basic Operation
The SM8172A is equipped with a series regulator that drives a maximum 450mA load current at a fixed 3.3V
output voltage.
12-1-2. Soft Start Function
A soft start circuit is built-in to prevent output voltage overshoot and inrush current at startup. The soft start
time is the interval during which the output current is limited internally in the IC, and is different from the
series regulator output voltage rise time. The time varies with the load current, output capacitance, and other
conditions.
12-1-3. Overcurrent Protection Function
The series regulator overcurrent protection function uses a foldback method. When the output current exceeds
the overcurrent protection circuit operating current limit value of 700mA (typ), the output current and output
voltage are dropped, and the output short-circuit current is 80mA (typ). Normal operation is restored when the
overcurrent condition is resolved.
3.3V (typ)
LDOUT
(regulator output)
Output short-circuit
current
80mA (typ)
Overcurrent protection
current
700mA (typ)
ILDOUT
(regulator output current)
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