ADM1175 datasheet(13/24 Pages) AD

Part #	ADM1175

Description	Hot Swap Controller and Digital Power Monitor with Convert Pin

Download	24 Pages

Scroll/Zoom	100%

Manufacturer	AD [Analog Devices]

Direct Link	http://www.analog.com

Logo

13 / 24 page

ADM1175

Rev. 0 | Page 13 of 24

OVERVIEW OF THE HOT SWAP FUNCTION

When circuit boards are inserted into a live backplane, discharged

supply bypass capacitors draw large transient currents from the

backplane power bus as they charge. Such transient currents can

cause permanent damage to connector pins, as well as dips on

the backplane supply that can reset other boards in the system.

The ADM1175 is designed to turn a circuit board supply voltage

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

be safely inserted into or removed from a live backplane. The

ADM1175 can reside either on the backplane or on the circuit

board itself.

The ADM1175 controls the inrush current to a fixed maximum

level by modulating the gate of an external N-channel FET placed

between the live supply rail and the load. This hot swap function

protects the card connectors and the FET itself from damage

and limits any problems that can be caused by high current loads

on the live supply rail.

The ADM1175 holds the GATE pin down (and, thus, the FET is

held off) until a number of conditions are met. An undervoltage

lockout circuit ensures that the device is provided with an adequate

input supply voltage. Once the input supply voltage has been

successfully detected, the device goes through an initial timing

cycle to provide a delay before it attempts to hot swap. This delay

ensures that the board is fully seated in the backplane before the

board is powered up.

Once the initial timing cycle is complete, the hot swap function

is switched on under control of the ON/ONB pin. When ON/ONB

is asserted (high for the ADM1175-1 and ADM1175-2, low for

the ADM1175-3 and ADM1175-4), the hot swap operation starts.

The ADM1175 charges up the gate of the FET to turn on the

load. It continues to charge up the GATE pin until the linear

current limit (set to 100 mV/RSENSE) is reached. For some combi-

nations of low load capacitance and high current limit, this limit

may not be reached before the load is fully charged up. If current

limit is reached, the ADM1175 regulates the GATE pin to keep

the current at this limit. For currents above the overcurrent fault

timing threshold, nominally 100 mV/RSENSE, the current fault is

timed by sourcing a current out to the TIMER pin. If the load

becomes fully charged before the fault current limit time is

reached (when the TIMER pin reaches 1.3 V), the current drops

below the overcurrent fault timing threshold. The ADM1175

then charges the GATE pin higher to fully enhance the FET for

lowest RON, and the TIMER pin is pulled down again.

If the fault current limit time is reached before the load drops

below the current limit, a fault has been detected, and the hot

swap operation is aborted by pulling down on the GATE pin to

turn off the FET. The ADM1175-2 and ADM1175-4 are latched

off. They attempt to hot swap again only when the ON/ONB pin is

deasserted and then asserted again.

The ADM1175-1 and ADM1175-3 retry the hot swap operation

indefinitely, keeping the FET in its safe operating area (SOA) by

using the TIMER pin to time a cool-down period in between

hot swap attempts. The current and voltage threshold combinations

on the TIMER pin set the retry duty cycle to 3.8%.

The ADM1175 is designed to operate over a range of supplies

from 3.15 V to 16.5 V.

UNDERVOLTAGE LOCKOUT

An internal undervoltage lockout (UVLO) circuit resets the

ADM1175 if the VCC supply is too low for normal operation.

The UVLO has a low-to-high threshold of 2.8 V, with 80 mV

hysteresis. Above 2.8 V supply voltage, the ADM1175 starts the

initial timing cycle.

ON/ONB FUNCTION

The ADM1175-1 and ADM1175-2 have an active high ON pin.

The ON pin is the input to a comparator that has a low-to-high

threshold of 1.3 V, a 50 mV hysteresis, and a glitch filter of 3 μs.

A low input on the ON pin turns off the hot swap operation by

pulling the GATE pin to ground, turning off the external FET.

The TIMER pin is also reset by turning on a pull-down current

on this pin. A low-to-high transition on the ON pin starts the

hot swap operation. A 10 kΩ pull-up resistor connecting the

ON pin to the supply is recommended.

Alternatively, an external resistor divider at the ON pin can be

used to program an undervoltage lockout value higher than the

internal UVLO circuit, thereby setting a voltage level at the

VCC supply, where the hot swap operation is to start. An RC

filter can be added at the ON pin to increase the delay time at

card insertion if the initial timing cycle delay is insufficient.

The ADM1175-3 and ADM1175-4 have an active low ONB pin.

This pin operates exactly as described above for the ON pin,

but the polarity is reversed. This allows this pin to function as

an overvoltage detector that can use the external FET as a circuit

breaker for overvoltage conditions on the monitored supply.

TIMER FUNCTION

The TIMER pin handles several timing functions with an

external capacitor, CTIMER. There are two comparator thresholds:

VTIMERH (0.2 V) and VTIMERL (1.3 V). The four timing current

sources are a 5 μA pull-up, a 60 μA pull-up, a 2 μA pull-down,

and a 100 μA pull-down. The 100 μA pull-down is a non-ideal

current source, approximating a 7 kΩ resistor below 0.4 V.

These current and voltage levels, together with the value of CTIMER

chosen by the user, determine the initial timing cycle time, the

fault current limit time, and the hot swap retry duty cycle.

Similar Part No. - ADM1175

Manufacturer	Part #	Datasheet	Description
Analog Devices	ADM1170	266Kb / 16P	1.6 V to 16.5 V Hot Swap Controller with Soft Start REV. 0
	ADM1170-1AUJZ-RL7	266Kb / 16P	1.6 V to 16.5 V Hot Swap Controller with Soft Start REV. 0
	ADM1170-2AUJZ-RL7	266Kb / 16P	1.6 V to 16.5 V Hot Swap Controller with Soft Start REV. 0
	ADM1170	248Kb / 16P	1.6 V to 16.5 V Hot Swap Controller with Soft Start REV. A
	ADM1171	255Kb / 16P	2.7 V to 16.5 V Hot Swap Controller with Current Sense Output REV. 0

More results

Similar Description - ADM1175

Manufacturer	Part #	Datasheet	Description
Analog Devices	ADM1176	683Kb / 24P	Hot Swap Controller and I2C짰 Power Monitor with Convert Pin REV. 0
	ADM1177	203Kb / 16P	Hot Swap Controller and Digital Power Monitor with Soft-Start Pin Rev. PrD May 2006
	ADM1177	583Kb / 24P	Hot Swap Controller and Digital Power Monitor with Soft Start Pin REV. C
	ADM1178	203Kb / 16P	Hot Swap Controller and Digital Power Monitor with AlertB Output Rev. PrD May 2006
	ADM1278	874Kb / 61P	Hot Swap Controller and Digital Power and Energy Monitor with PMBus Interface
	ADM1191	389Kb / 16P	Digital Power Monitor with Convert Pin and ALERTB O REV. 0
	EVAL-ADM1275EBZ	741Kb / 48P	Hot-Swap Controller and Digital Power REV. D
	ADM1272	578Kb / 57P	High Voltage Positive Hot Swap Controller and Digital Power Monitor with PMBus
	ADM1191	403Kb / 16P	Digital Power Monitor with Convert Pin and ALERTB Output REV. B
	LTC4287	2Mb / 77P	High Power Positive Hot Swap Controller with Power Monitor Rev. 0

More results

ADM1175 Datasheet(PDF) 13 Page - Analog Devices

ADM1175 Datasheet(HTML) 13 Page - Analog Devices

Similar Part No. - ADM1175

Similar Description - ADM1175

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Datasheet Download

Link URL