TPS65166 datasheet(17/41 Pages) TI1

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Start-Up Sequencing

EN2

Vlogic

VOFFE

EN1

VIN

VONE

VSS

GDok

DLY1

DLY2

DLY2<DLY1

DLY2>DLY1

PowerGoodfor

ScanDriveIC

Power Good Output

TPS65166

www.ti.com.......................................................................................................................................................................................... SLVS976 – SEPTEMBER 2009

The buck converter detects a short circuit if FB2 falls below 400 mV and the whole device except the buck

converter itself is shut down as if EN2 would be disabled. The switching frequency of the buck converter is

reduced to 1/4th of the normal operation frequency. If the short is removed the buck converter will start operation

again and the whole device auto recovers to normal operation by doing startup sequencing as if EN2 would be

enabled.

The negative buck boost converter VOFFE has a short circuit protection where the switch current is limited to

typically 300 mA and switching frequency is reduced to about 150 kHz. A short is detected if VOFFE rises above

-3 V.

The shunt regulator Vss has no short circuit protection.

The device has adjustable start-up sequencing to provide correct sequencing as required by the display.

Figure 23. Power Up Sequencing

EN1 enables the buck converter.

EN2 enables the negative buck boost converter VOFFE and Vss at the same time. DLY1 sets the delay time for the

boost converter Vs and DLY2 sets the delay time for VONE. VONE does not start until DLY1 is elapsed. For

simultaneous startup of Vs and VONE, DLY2 should be set to 0 by not connecting the DLY2 pin. Once VS and

VONE are in regulation, PG goes high impedance to enable the scan driver IC.

The power good output PG is an open drain output with typically 450

Ω resistance and requires a pull-up resistor

to the 3.3V rail. The power good goes high impedance when the Vs and VONE voltage rails are in regulation and

provides an enable signal for the external scan driver IC. Once power good is high impedance, the signal is

latched until Vs or VONE detect a short circuit.

The resulting maximum PG voltage if PG is low is dependent on R22 connection voltage (Vlogic) and R22 value.

To calculate maximum resulting PG voltage for power bad signal use following formula:

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