RT9629B datasheet(4/14 Pages) RICHTEK

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RT9629B

DS9629B-06

July 2015

www.richtek.com

is a registered trademark of Richtek Technology Corporation.

Operation

POR (Power On Reset)

POR block detects the voltage at VCC1 pin and VCC2

pin. When the VCC1 and VCC2 pin voltage is higher than

POR rising threshold, POR pin output voltage (POR

output) is high. POR output is low when VCC1 and VCC2

are not both higher than POR rising threshold. When the

POR pin voltage is high, UGATEx and LGATEx can be

controlled by PWMx pin voltage. With low POR pin voltage,

both UGATEx and LGATEx will be pulled to low.

Tri-State Detect

When the POR block output voltage is high, UGATEx

and LGATEx can be controlled by PWMx input. There are

three PWMx input modes, which are high, low, and

shutdown state. If PWMx input is within the shutdown

window, both UGATEx and LGATEx output are low. When

PWMx input is higher than its rising threshold, UGATEx

is high and LGATEx is low. When PWMx input is lower

than its falling threshold, UGATEx is low and LGATEx is

high.

Bootstrap Control

Bootstrap control block controls the integrated bootstrap

switch. When LGATEx is high (low side MOSFET is

turned on), the bootstrap switch is turned on to charge

the bootstrap capacitor connected to BOOTx pin. When

LGATEx is low (low side MOSFET is turned off), the

bootstrap switch is turned off to disconnect VCCx pin and

BOOTx pin.

Turn-Off Detection

Turn-off detection block detects whether high side

MOSFET is turned off by monitoring PHASEx pin voltage.

To avoid shoot through between high side and low side

MOSFETs, low side MOSFET can be turned on only after

high side MOSFET is effectively turned off.

Shoot-Through Protection :

Shoot-through protection block implements the dead time

when both high side and low side MOSFETs are turned

off. With shoot-through protection block, high side and

low side MOSFET are never turned on simultaneously.

Thus, shoot through between high side and low side

MOSFETs is prevented.

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