RT8205M datasheet(22/26 Pages) RICHTEK

22 / 26 page

RT8205L/M

DS8205L/M-05 June 2011

www.richtek.com

(a). Start-Up at the Same Time

(b). Delay Start Mode

Figure 5. Time Diagrams of Power Sequence

Table 2. Operation Mode Truth Table

Mode

Condition

Comment

Power UP

VREGX < UVLO threshold

Transitions to discharge mode after a VIN POR and after

REF becomes valid. VREG5, VREG3, and REF remain

active.

RUN

EN = high, VOUT1 or VOUT2

enabled

Normal Operation.

Over Voltage

Protection

Either output > 111% of the nominal

level.

LGATEx is forced high. VREG3, VREG5 and REF active.

Exited by VIN POR or by toggling EN, ENTRIPx

Under

Voltage

Protection

Either output < 52% of the nominal

level after 3ms time out expires and

output is enabled

Both UGATEx and LGATEx are forced low and enter

discharge mode. VREG3, VREG5 and REF are active.

Exited by VIN POR or by toggling EN, ENTRIPx

Discharge

Either SMPS output is still high in

either standby mode or shutdown

mode

During discharge mode, there is one path to discharge the

outputs capacitor residual charge. That is output capacitor

discharge to GND through an internal switch.

Standby

ENTRIPx < startup threshold,

EN = high.

VREG3, VREG5 and REF are active.

Shutdown

EN = low

All circuitry off.

Thermal

Shutdown

TJ > 150°C

All circuitry off. Exit by VIN POR or by toggling EN, ENTRIPx

VENTRIPx

VENTRIPy

< 60µs

VOUTx

VOUTy

0.515V

VOUTx

> 60µs

0.515V

VOUTy

2ms

VENTRIPx

VENTRIPy

≈

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