LTC1646IGN datasheet(9/20 Pages) LINER

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LTC1646

1646fa

Hot Circuit Insertion

When a circuit board is inserted into a live CompactPCI

(CPCI) slot, the supply bypass capacitors on the board can

draw huge supply transient currents from the CPCI power

bus as they charge up. The transient currents can cause

glitches on the power bus, causing other boards in the

system to reset.

The LTC1646 is designed to turn a board’s supply voltages

on and off in a controlled manner, allowing the board to be

safely inserted or removed from a live CPCI slot without

glitching the system power supplies. The chip also pro-

tects the supplies from shorts, precharges the bus I/O pins

during insertion and extraction and monitors the supply

voltages.

BLOCK DIAGRA

TIMER 2

3VOUT

5VOUT

–

+–

200

µA

GATE

5VOUT

55mV

150mV

VGG

5VSENSE

5VIN

–

+–

2.5V

UVL

–

+–

3VOUT

55mV

150mV

CP3

REF

3VSENSE

3VIN

RESETOUT

–

+–

2.5V

UVL

CP4

REF

–

RESETIN 16

PWRGD 4

FAULT 3

OFF/ON 15

µA

5Vin

GND

DRIVE

PRECHARGE

1646 BD

LOGIC

APPLICATIO S I FOR ATIO

The LTC1646 is specifically designed for CPCI applica-

tions where the chip resides on the plug-in board.

LTC1646 Feature Summary

1. Allows safe board insertion and removal from a CPCI

backplane.

2. Controls 5V and 3.3V CPCI supplies.

3. Current limit during power-up: the supplies are allowed

to power up in current limit. This allows the chip to

power up boards with widely varying capacitive loads

without tripping the circuit breaker. The maximum

allowable power-up time is programmable using the

TIMER pin and an external capacitor.

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