AP74502Q, AP74502HQ

Document number: DS47093 Rev. 1 - 2

17 of 22

www.diodes.com

April 2025

© 2025 Copyright Diodes Incorporated. All Rights Reserved.

AP74502Q, AP74502HQ

, AP

Application Information (continued)

Fast Turn-On and Turn-Off High Side Switch Driver Using the AP74502HQ

In automotive load driving applications N-Channel MOSFET based high side switch is very commonly used to disconnect the loads from supply line

in case of faults such as overvoltage event. The AP74502Q, AP74502HQ can be used to drive external MOSFET to perform simple high side switch

with overvoltage protection. Below diagram shows a typical application circuit where the AP74502HQ is used to drive external MOSFET Q1 as a

switch for main power path control. A resistor divider from input to OVLO pin to ground can be used to set the overvoltage threshold.

If VOUT node (SRC pin) of the device is expected to drop in case of events such as overcurrent or short-circuit on load side, then additional Zener

diode is required across gate and source pin of external MOSFET to protect it from exceeding its maximum VGS rating.

AP74502HQ

GATE

SRC

OVLO

VCAP

GND

Load1

Q1

10uF

Battery /

Power

Source

VI N

R1

R2

EN/UVLO

ON

OFF

VOUT

VI N

ON

OFF

FAST ON/OFF

Transition

Load2

Load3

Many safety applications require fast switching off of the MOSFET in case of fault events such as overvoltage or overcurrent fault. Some of the load

driving path applications also require PWM operation of high side switch. The AP74502HQ OVLO pin can be used as control input to perform fast

turn-on and turn-off mode transition. With OVLO pin pulled above VOVR threshold of (1.25V typical), the AP74502HQ turns off the external MOSFET

(with CISS = 4.7nF) within 1μs typically. When OVLO pin is pulled low, the AP74502HQ with its peak gate drive strength of 11mA turns on external

MOSFET with turn-

on speed of 7μs typical.

Time [200µs/Div]

Fast Turn-On and Turn-Off High Side Switch Driver Using AP74502HQ

Power Supply Recommendations

The AP74502Q, AP74502HQ reverse polarity protection controller is designed for the supply voltage range

of 3.2V ≤ VS ≤ 80V. If the input supply

is located more than a few inches from the device, we recommend an input cerami

c bypass capacitor higher than 0.1μF. Based on system

requirements, a higher input bypass capacitor can be needed with the AP74502HQ to avoid supply glitch in case of high inrush current start-up

event. To prevent the AP74502Q, AP74502HQ and surrounding components from damage under the conditions of a direct output short circuit, use

a power supply having overload and short-circuit protection.

OV pin is pulled high and GATE to SRC

Is pulled low (within 1µs typical)

OV pin is pulled low and

GATE to SRC is pulled high

VOV

2V/div

VGATE

- VSRC

10V/div

1

0μF