RT5788A/B
smooth start-up. The typical soft-start time is 1.5ms.
Power Good Indication
The RT5788A/B provides a power-good (PGOOD) open-
drain output pin. It is to be connected to an external voltage
source through a pull-up resistor. The power-good function
is activated after soft-start is finished and is controlled by
a comparator connected to the feedback signal VFB. If
VFB rises above a power-good threshold (VTH_PGLH
)
(typically 95% of the target value), the PGOOD pin will be
in high impedance and VPGOOD will be held high after a
certain delay elapsed. When VFB drops by a power-good
hysteresis (ΔVTH_PGLH) (typically 5% of the target value)
or exceeds VTH_PGHL (typically 110% of the target value),
the PGOOD pin will be pulled low. For VFB higher than
VTH_PGHL, VPGOOD can be pulled high again if VFB drops
back by a power-good hysteresis (ΔVTH_PGHL) (typically
5% of the target value). Once being started-up, if any
internal protection is triggered, PGOOD will be pulled low
toGND.
Over-Temperature Protection (Thermal Shutdown)
The RT5788A/B includes an over-temperature protection
(OTP) circuitry to prevent overheating due to excessive
power dissipation. The OTP will shut down switching
operation when junction temperature exceeds a thermal
shutdown threshold TSD. Once the junction temperature
cools down by a thermal shutdown hysteresis (ΔTSD), the
IC will resume normal operation with a complete soft-start.
Copyright 2018 Richtek Technology Corporation. All rights reserved.
©
is a registered trademark of Richtek Technology Corporation.
DS5788A/B-02 March 2018
www.richtek.com
5
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