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FDC6323L

Integrated Load Switch

ON Semiconductor 

FDC6323L Load Switch Application

APPLICATION CIRCUIT

Q2

IN

R1

C1

OUT

O N / O FF

Q1

Co

LOAD

R2

General Description

This device is particularly suited for compact

computer peripheral switching applications

where 8V input and 1A output current capability

are needed. This load switch integrates a small

N-Channel Power MOSFET (Q1) which drives a

large P-Channel Power MOSFET (Q2) in one

tiny SuperSOTTM-6 package.

A load switch is usually configured for high side

switching so that the load can be isolated from

the active power source. A P-Channel Power

MOSFET, because it does not require its drive

voltage above the input voltage, is usually more

cost effective than using an N-Channel device in

this particular application. A large P-Channel

Power MOSFET minimizes voltage drop. By

using a small N-Channel device the driving

stage is simplified.

Component Values

R1

Typical 10k - 1MΩ

R2

Typical 0 - 100kΩ (optional)

C1

Typical 1000pF (optional)

Design Notes

R1 is needed to turn off Q2.

R2 can be used to soft start the switch in case the output capacitance Co is small.

R2 should be at least 10 times smaller than R1 to guarantee Q1 turns on.

By using R1 and R2 a certain amount of current is lost from the input. This bias current loss is given by

the equation

= I BIAS_LOSS

Vin

R 1 +R2

when the switch is ON. IBIAS_LOSS can be minimized by selecting a large

value for R1.

R2 and CRSS of Q2 make ramp for slow turn on. If excessive overshoot current occurs due to fast turn on,

additional capacitance C1 can be added externally to slow down the turn on.

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