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AAT4684

Over-Voltage Protection Switch

DATA SHEET

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com

201959A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • May 16, 2012

Over-Voltage Protection

The AAT4684 adjustable version has a 1.1V 1.5% over-

voltage trip threshold on the OVP pin. With a resistor

divider on OVP pin from IN to GND, the over-voltage trip

point can be adjusted anywhere within the input voltage

range (see Table 1). Once the over-voltage trip level is

triggered, the PMOS switch controller will shut off the

PMOS in less than 1μs.

The AAT4684 fixed version is also available where the

resistor divider is internally integrated with the input

voltage trip point at 6.5V. The fixed version of AAT4684

does not have a connection to the internal OVP circuitry

and the pin #11 is designed to be not connected.

FLT Output

The FLT output is an active-low open-drain fault (OV)

reporting output. A pull-up resistor should be connected

from FLT to the logic I/O voltage of the host system. FLT

will be asserted immediately if an over-voltage fault

occurs (only about a 1μs inherited internal circuit delay).

A 10ms blanking is applied to FLT signal prior to de-

assertion.

Over-Temperature Protection (OTP)

the OVP switch is turned off, and the pin is driven low.

The OVP switch will recover automatically when the

EN Input

EN is an active-low enable input. EN is driven low, con-

nected to ground, or left floating for normal device

operation. Taking the EN high turns off the MOSFET. In

the case of an over-voltage or UVLO condition toggling

the EN will not override the fault condition and the

switch will remain off.

Device Operation

10ms internal delay.

Application Information

Over-Voltage Protection

The AAT4684 over-voltage protection circuit provides

fast protection against transient voltage spikes and short

duration spikes of high voltage from the power supply

lines. AAT4684 can quickly disconnect the input supply

from the load and not cause any damage to sensitive

components

In portable product applications, if the user removes the

battery pack during charging, this action can create

large transients and a high voltage spike can occur

which can damage other electronic devices in the prod-

uct such as the battery charger. A hot plug of the AC/DC

wall adapter into the AC outlet can create and release a

voltage spike from the transformer. As a result, some

sensitive devices within the product can be damaged.

With the AAT4684 placed between the power lines and

the sensitive devices, the voltage spike can be kept

away and the input supply disconnected from other

devices in 0.7μs.

Figure 2 shows the response time of over-voltage pro-

tection from the test circuit (Figure 1). The input volt-

age is rapidly increased from 5V to 12V by a voltage

surge or voltage spike. The voltage at the OVP pin is also

increased until the trip point is triggered. At this point,

the FLT pin is pulled low and the output voltage starts to

fall. Figure 3 shows a zoom-in scope capture of the OVP

response time; the output is disconnected from the input

in as little as 700ns.

Adjustable Version -

Over-Voltage Protection Resistors

The over-voltage protection threshold is programmed

with two resistors, R1 and R2. To limit the current going

through the external resistor string while maintaining

good noise immunity, use smaller resistor values, such

as 10KΩ for R2. Using a larger value will further reduce

the system current, but will also increase the impedance

of the OVP node, making it more sensitive to external

noise and interference.

V

R

1

R

2