MAX8819A/MAX8819B/MAX8819C
PMIC with Integrated Chargers and Smart
Power Selector in a 4mm x 4mm TQFN
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As the load current is increased beyond this point, the
output voltage sags and the converter goes out of regu-
lation because the inductor current cannot increase
above the p-channel peak current limit.
Step-Down Converter Short-Circuit Protection
The step-down converter implements short-circuit protec-
tion by monitoring the feedback voltage, V
FB_
. After soft-
start, if V
FB_
drops below 0.23V, the converter reduces its
switching frequency to f
S
/3. The inductor current still
reaches the p-channel peak current limit, however, at
one-third the frequency. Therefore, the output and input
currents are reduced to approximately one-third of the
maximum value in response to an output short circuit to
ground. When the short is removed, the inductor current
raises the voltage on the output capacitor and the step-
down converter resumes normal operation.
REG1 Reset (RST1)
RST1 is an active-low, open-drain output that pulls low
to indicate that FB1 is below its regulation threshold.
RST1 goes high 200ms after FB1 reaches its regulation
threshold. RST1 is high-impedance when EN123 is
high. See Figures 6 and 7.
A 50μs blanking delay is provided when FB1 is falling,
so that RST1 does not glitch if the REG1 output voltage
is dynamically adjusted by altering the resistors in its
feedback network.
