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Document Number: 63315

S11-1695-Rev. B, 22-Aug-11

Vishay Siliconix

SiP32452, SiP32453

This document is subject to change without notice.

DETAILED DESCRIPTION

SiP32452 and SiP32453 are n-channel power MOSFET

designed as high side load switch. Once enable the device

charge pumps the gate of the power MOSFET to a constant

gate to source voltage for fast turn on time. The mostly

constant gate to source voltage keeps the on resistance low

through out the input voltage range. When disable, the

SiP32452 pulls the gate of the output n-channel low right

away for a fast turn off delay while there is a build-in turn off

delay for the SiP32453. The turn off delay for the SiP32453

is guaranteed to be at least 30 µs. Because the body of the

output n-channel is always connected to GND, it prevents

the current from going back to the input in case the output

voltage is higher than the output.

APPLICATION INFORMATION

Input Capacitor

While a bypass capacitor on the input is not required,

all applications. The bypass capacitor should be placed as

physically close as possible to the input pin to be effective in

minimizing transients on the input. Ceramic capacitors are

recommended over tantalum because of their ability to

withstand input current surges from low impedance sources

such as batteries in portable devices.

Output Capacitor

to insure proper slew operation. There is inrush current

through the output MOSFET and the magnitude of the inrush

the higher the inrush current. There are no ESR or capacitor

type requirement.

Enable

The EN pin is compatible with CMOS logic voltage levels. It

requires at least 0.1 V or below to fully shut down the device

and 1.5 V or above to fully turn on the device.

Protection Against Reverse Voltage Condition

Both the SiP32452 and SiP32453 can block the output

current from going to the input in case where the output

voltage is higher than the input voltage when the main switch

is off.

Thermal Considerations

These devices are designed to maintain a constant output

load current. Due to physical limitations of the layout and

assembly of the device the maximum switch current is 1.2 A

as stated in the Absolute Maximum Ratings table. However,

another limiting characteristic for the safe operating load

current is the thermal power dissipation of the package. To

obtain the highest power dissipation (and a thermal

resistance of 280 °C/W) the device should be connected to a

heat sink on the printed circuit board.

The maximum power dissipation in any application is

dependant

on

the

maximum

junction

temperature,



may be formulaically expressed as:

It then follows that, assuming an ambient temperature of

70 °C, the maximum power dissipation will be limited to about

196 mW.

So long as the load current is below the 1.2 A limit, the

maximum continuous switch current becomes a function two

ambient temperature.

As an example let us calculate the worst case maximum load

65 m

. The R

data using the following formula:

we have

= 76.4 m



The maximum current limit is then determined by

which in case is 1.6 A. Under the stated input voltage

condition, if the 1.6 A current limit is exceeded the internal die

temperature will rise and eventually, possibly damage the

device.

To avoid possible permanent damage to the device and keep

a reasonable design margin, it is recommended to operate

the device maximum up to 1.2 A only as listed in the

Absolute Maximum Ratings table.

280

125

(max.)

(max.)

A

A

J

A

J

T

T

T

P

-

=

-

=

-

θ

)

(

(max.)

(max.)

ON

DS

LOAD

R

P

I

<