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ADM1070

–48 V Hot Swap Controller

FUNCTIONAL BLOCK DIAGRAM

REFERENCE

GENERATOR

OVER-UNDER

VOLTAGE DETECTION

CIRCUIT

FAULT TIMER AND

CONTROL

OSCILLATOR

SENSE

0V

R1

R2

–48V

UV/OV

TIMER

12V

16k

EN

100mV

45 A

GATE

()*

*OPTIONAL TIMER CAPACITOR

ADM1070

Q1

FEATURES

Allows Safe Board Insertion and Removal from a Live

–48 V Backplane

Typically Operates from –36 V to –80 V

Tolerates Transients up to –200 V (Limited by External

Components)

Accurate Programmable Linear Current Limit for

In-Rush Control and Short Circuit Protection

Programmable Timeout in Current Limit

Limited Consecutive Retry:

Auto-Restart after Current Limit Timeout

Shutdown after Seven Consecutive Auto Restarts

Provides Immunity from Step Induced Current Spikes

Default Timing Provided with no TIMER Capacitor

Single Pin Undervoltage/Overvoltage Detection

Programmable Operating Voltage Window

Programmable Undervoltage/Overvoltage Time Filter

Small 6-Lead SOT-23 Package

APPLICATIONS

Central Office Switching

–48 V Distributed Power Systems

Negative Power Supply Control

Hot Board Insertion

Electronic Circuit Breaker

High Availability Servers

Programmable Current Limiting Circuit

–48 V Power Supply Modules

GENERAL DESCRIPTION

The ADM1070 is a negative voltage hot swap controller that

allows a board to be safely inserted and removed from a live

–48 V backplane. The part achieves this by providing robust

current limiting, protection against transient and nontransient

short circuits and overvoltage and undervoltage conditions. The

ADM1070 typically operates from a negative voltage of up to

–80 V and can tolerate transient voltages of up to –200 V.

In-rush current is limited to a programmable value by control-

ling the gate drive of an external N-channel FET. The current

limit can be controlled by the choice of the sense resistor,

on-chip timer that uses pulsewidth modulation to allow the

maximum current to flow for only 3% of the time. An autorestart

occurs after a current limit timeout. After seven successive

autorestarts, the fault will be latched and the part goes into

shutdown with the result that the external FET is disabled until

the power is reset.

The ADM1070 also features single-pin undervoltage and over-

voltage detection. The FET is turned off if a nontransient

voltage less than the undervoltage threshold, typically –36 V, or

greater than the overvoltage threshold, typically –77 V, is detected

on the UV/OV Pin. The operating voltage window of the

ADM1070 is programmable and is determined by the ratio R1/R2.

Time filtering on the undervoltage and overvoltage detection

and current limiting is programmable via the TIMER Pin. An

determines the undervoltage/overvoltage time filter and the

values and the current limit timeout revert to default figures.

The ADM1070 is fabricated using BiCMOS technology for mini-

mal power consumption. The part is available in a small

6-Lead SOT-23 package.