RT5789A/B
Power Good Indication
The RT5789A/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 V
FB
. If
V
FB
rises above a power-good threshold (V
TH_PGLH
)
(typically 95% of the target value), the PGOOD pin will be
in high impedance and V
PGOOD
will be held high after a
certain delay elapsed. When V
FB
drops by a power-good
hysteresis (ΔV
TH_PGLH
) (typically 5% of the target value)
or exceeds V
TH_PGHL
(typically 110% of the target value),
the PGOOD pin will be pulled low. For V
FB
higher than
V
TH_PGHL
, V
PGOOD
can be pulled high again if V
FB
drops
back by a power-good hysteresis (ΔV
TH_PGHL
) (typically
5% of the target value). Once being started-up, if any
internal protection is triggered, PGOOD will be pulled low
to GND.
Over-Temperature Protection (Thermal Shutdown)
The RT5789A/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 T
SD
. Once the junction temperature
cools down by a thermal shutdown hysteresis (ΔT
SD
), 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.
www.richtek.com
6
DS5789A/B-02 March 2018
RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
