Vishay Siliconix

SiP4280

Document Number: 73476

S-61690–Rev. D, 04-Sep-06

www.vishay.com

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BLOCK DIAGRAM

DETAILED DESCRIPTION

The SiP4280 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 increased to the full input voltage to reduce

associated power losses.

The SiP4280-1 version has a modest 1 ms turn on

slew rate feature, which significantly reduces in-rush

current at turned on time and permits the load switch

to be implemented with a small input capacitor, or no

input capacitor at all, saving cost and space. In addi-

tion to a 100 µs minimized slew rate, the SIP4280-3

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.

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.

SiP4280 Functional Block Diagramm

SiP4280–3 Version only