RT6214A/B
after this ramp voltage is greater than the feedback
voltage VFB to ensure the converters have a smooth
start-up. For soft-start control, the SS pin should never
be left unconnected.
External Bootstrap Capacitor
Connect a 0.1F low-ESR ceramic capacitor between
the BOOT and LX pins. This bootstrap capacitor
supplies for the gate driver of the high-side N-channel
MOSFET switch.
Power Good Indication
(For RT6214A/BHRGJ8F)
Over-Temperature Protection (Thermal Shutdown)
The PGOOD pin is an open-drain output and is
connected to an external pull-up resistor. It is controlled
by a comparator, which the feedback signal VFB is fed
to. If VFB is above 90% of the internal reference voltage
after soft-start finished, the PGOOD pin will be in high
impedance and VPGOOD will be held high. Otherwise,
the PGOOD output will be pulled low.
The RT6214A/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 (TSD), the IC will resume normal
operation with a complete soft-start.
Soft-Start (SS)
(For RT6214A/BHRGJ6F)
The soft-start function is used to prevent large inrush
currents while the converter is being powered up. The
RT6214A/B provides an internal soft-start feature for
inrush control. During the start-up sequence, the
internal capacitor is charged by an internal current
source ISS to generate a soft-start ramp voltage as a
reference voltage to the PWM comparator. The device
will initiate switching and the output voltage will
smoothly ramp up to its targeted regulation voltage only
after this ramp voltage is greater than the feedback
voltage VFB to ensure the converters have a smooth
start-up. The typical soft-start time is 1ms.
Soft-Start (SS)
(For RT6214A/BHRGJ8F)
The soft-start function is used to prevent large inrush
currents while the converter is being powered up. The
RT6214A/B provides a soft-start feature for inrush
control. It provides an SS pin so that the soft-start time
can be programmed by selecting the value of the
external capacitor CSS connected from the SS pin to
GND. During the start-up sequence, the external
capacitor is charged by an internal current source ISS
(typically, 6A) to generate a soft-start ramp voltage as
a reference voltage to the PWM comparator. The
device will initiate switching and the output voltage will
smoothly ramp up to its targeted regulation voltage only
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DS6214A/B-04 August 2017
RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
