SiP4282, SiP4282A

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Vishay Siliconix

S20-0532-Rev. H, 06-Jul-2020

8

Document Number: 65740

THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT

DETAILED DESCRIPTION

The SiP4282 is a p-channel MOSFET power switches

designed for high-side slew rate controlled load-switching

applications. Once turned on, the slew-rate control circuitry

is activated and current is ramped in a linear fashion until it

reaches the level required for the output load condition. This

is accomplished by first elevating the gate voltage of the

MOSFET up to its threshold voltage and then by linearly

increasing the gate voltage until the MOSFET becomes fully

enhanced. At this point, the gate voltage is then quickly

MOSFET switch and minimize any associated power losses.

All versions features a shutdown output discharge circuit

which is activated at shutdown (when the part is disabled

through the on / off pin) and discharges the output pin

through a small internal resistor hence, turning off the load.



For SiP4282-3, in instances where the input voltage falls

below 1.4 V (typically) the under voltage lock-out circuitry

protects the MOSFET switch from entering the saturation

region or operation by shutting down the chip.

APPLICATION INFORMATION

Input Capacitor

While a bypass capacitor on the input is not required, a 1 μF

applications. The bypass capacitor should be placed as

physically close as possible to the SiP4282 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

be increased without limit to accommodate any load

transient condition with only minimal affect on the SiP4282

turn on slew rate time. There are no ESR or capacitor type

requirement.

Enable

The on / off pin is compatible with both TTL and CMOS logic

voltage levels.

Protection Against Reverse Voltage Condition

The p-channel MOSFET pass transistor has an intrinsic

diode that is reversed biased when the input voltage is

this intrinsic diode will become forward biased and allow

potentially damage the IC device. Therefore extreme care

parallel with the internal intrinsic diode is recommended to

protect the SiP4282.

Thermal Considerations

The SiP4282 is 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 90 °C/W) the power pad of the device

should be connected to a heat sink on the printed circuit

board.

The maximum power dissipation in any application is

dependent

on

the

maximum

junction

temperature,

resistance for the SC-75 PPAK package,



and

the

ambient

temperature,

formulaically expressed as:

It then follows that, assuming an ambient temperature of

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

about 610 mW.

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

maximum continuous switch current becomes a function

the ambient temperature.

As an example let us calculate the worst case maximum

occurs at an input voltage of 1.8 V and is equal to 480 m

.

the following formula

we have

551 m



The maximum current limit is then determined by

which in case is 1.05 A. Under the stated input voltage

condition, if the 1.05 A current limit is exceeded the internal

die temperature will rise and eventually, possibly damage

the device.

P (max.)

T



J-A

-------------------------------------

125 - T

A

90

-----------------------

==

I

P (max.)

R

DS(on)

-----------------------

