AN2603 datasheet(8/23 Pages) STMICROELECTRONICS

8 / 23 page

ST1S09 description

AN2603

8/23

Doc ID 13778 Rev 3

If the output voltage is fixed using an external or internal resistor divider, the Power Good

threshold is 0.92*VOUT.

The use of the Power Good function requires an external pull-up resistor, which must be

connected between the PG pin and VIN or VOUT. The typical current capability of the PG pin

is up to 6 mA. The use of a pull-up resistor for PG in the range of 100 k

Ω to 1 MΩ is

recommended. If the Power Good function is not used, the PG pin must remain floating in

the board.

In the application board, R3 is used to pull up the PG pin to VIN and R4 to pull up the PG pin

to VOUT. The Power Good pin can be connected only to VIN or VOUT.

Figure 8.

Power Good

1.3

Over voltage protection

When output voltage is over 10% of the nominal value, a small NMOS is turned on to

discharge the output. The limitation of the clamping current is about 300 mA.

When the output voltage drops below 1.05*Vout, the device returns to normal closed loop

switching operation.

VOUT

(VIN=5 V, VOUT=3.18 V,

R3=120 k

Ω ch1=PG, ch3=V

OUT)

AN2603 Datasheet(PDF) 8 Page - STMicroelectronics