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AAT4620

PCMCIA Current Limit Interface and Capacitor Charger

Advanced Analogic Technologies 

AAT4620

PCMCIA Current Limit Interface

and Capacitor Charger

Functional Block Diagram

VCC

EN IL

EN IU

Reverse

Blocking

Under-

Voltage

Lockout

Over-Temp

Protection

Power

Loop

OUT

RDY

1.2V

Reference

Current Limit

Control

ISETL

ISETU

GND

RHYS

Functional Description

The AAT4620 is an integrated P-channel MOSFET

load switch with an upper and lower adjustable cur-

rent limits which can be enabled independently,

over temperature protection, a power loop and a

super capacitor charger. The current limit control is

combined with an over temperature thermal limit

and power loop circuit to provide a comprehensive

system to protect the load switch and its supply

from load conditions which exceed the supply spec-

ifications. The AAT4620 has been designed specif-

ically to provide the interface between a PCMCIA

host and PCMCIA card where a super capacitor has

been used to "average out" high pulse currents

which would otherwise exceed the PCMCIA/

Express Card power specifications. e.g. GSM/

GPRS modem cards, where pulse currents during

transmit signals can exceed the 1A maximum spec-

ification (1.3A in the case of Express Card).

The current limit and over temperature circuits act

independently. The device current limit is activated

when the output load current exceeds an internal

threshold level. There are two internal current lim-

its which are enabled independently. The current

limit threshold in each case is determined by exter-

4620.2007.04.1.1

9

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