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FPF2140/42/43/44/46/47 Rev. D

Application Notes

Power good function in sequential startup. No battery is loaded to the output

Power Good

FPF214X family has a "Power Good" feature. PGOOD pin is an

open-drain MOSFET which asserts high when the output

voltage reaches 90% of the input voltage.

PGOOD pin requires an external pull up resistor that is

connected to the output voltage when there is no battery in the

load side and the logic level of the subsequent controller

permits. This would give logic levels similar to a CMOS output

stage for PGOOD, while still keeping the option to tie the pull-up

to a different supply voltage. A typical value of 100KΩ is

recommended to be used as pull up resistor. The PGOOD pin

status is independent of the ON pin position. This mean that

PGOOD pin stays low when the load switch is OFF. If the Power

Good feature is not used in the application the pin can be

connected directly to GND.

Sequential Startup using Power Good

The power good pin can be connected to another load switch's

enable pin to implement sequential startup. PGOOD pin asserts

low when the load switch is OFF. This feature allows driving a

subsequent circuit. The above diagram illustrates power good

switch starts to ramp to the 90% of its input voltage the second

90% threshold, power good signal becomes active and asserts

will start to increase. The total startup time may vary according

to the difference between supply voltages that are used in the

application.

OFF ON

ON

GND

FPF2140/2/

3/4/6/7

FLAGB

To Load

Startup Power Sequence

PGOOD

100KΩ

ON

GND

FLAGB

To Load

PGOOD

100KΩ

FPF2140/2/

3/4/6/7

TP