MP1498 – SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS
Startup and Shutdown
If both VIN and EN exceed their respective
thresholds, the chip starts. The reference block
starts first, generating stable reference voltage
and currents, and then the internal regulator is
enabled. The regulator provides stable supply
for the remaining circuitries. The frequency
needs to fold-back linearly with FB so VOUT
starts up smoothly.
Three events can shut down the chip: EN low,
VIN low, and thermal shutdown. For the
shutdown procedure, the signaling path is first
blocked to avoid any fault triggering. The
COMP voltage and the internal supply rail are
then pulled down. The floating driver is not
subject to this shutdown command.
MP1498 Rev. 1.01
12/18/2012
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