RT8239A/B/C

21

DS8239A/B/C-06 October 2012

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Copyright 2012 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

Table1. Operation Mode Truth Table

Mode

Condition

Comment

Power Up

LDOx < UVLO threshold

Transitions to discharge mode after VIN POR and

after REF becomes valid. LDO5 and LDO3 remain

active.

Run

enabled

Normal Operation.

Over Voltage

Protection

Either output > 112% of the nominal level.

LGATEx is forced high. LDO3 and LDO5 are active.

Exit by VIN POR or by toggling ENLDO, ENTRIPx,

and ENM.

Under Voltage

Protection

Either output < 58% of the nominal level

after 3ms time-out expires and output is

enabled

Both UGATEx and LGATEx are forced low and

enter discharge mode. LDO3 and LDO5 are active.

Exit by VIN POR or by toggling ENLDO, ENTRIPx,

and ENM.

Discharge

Either output is still high in standby mode

or shutdown mode

During discharge mode, there is one path to

discharge the output capacitors’ residual charge to

GND via an internal switch.

Standby

ENTRIPx or ENM < startup threshold,

ENLDO = high.

LDO3 and LDO5 are active.

Shutdown

ENLDO = low

All circuitry are off.

Thermal

Shutdown

All circuitry are off. Exit by VIN POR or by toggling

ENLDO, ENTRIPx, and ENM.

Table 2. Power up Sequencing (RT8239A)

ENLDO (V)

ENM (V)

ENTRIP1

(V)

ENTRIP2

(V)

LDO5

LDO3

SMPS1

SMPS2

Low

Low

X

X

Off

Off

Off

Off

“>1.6V”

=> High

Low

X

X

On

On

Off

Off

“>1.6V”

=> High

“>2.3V”

=> High

Off

Off

On

On

Off

Off

“>1.6V”

=> High

“>2.3V”

=> High

Off

On

On

On

Off

On

“>1.6V”

=> High

“>2.3V”

=> High

On

On

On

On

On

On

“>1.6V”

=> High

“>2.3V”

=> High

On

Off

On

On

On

Off