LTC4236 datasheet(12/24 Pages) LINER

12 / 24 page

LTC4236

4236f

For more information www.linear.com/LTC4236

High availability systems often employ parallel-connected

powersuppliesorbatteryfeedstoachieveredundancyand

enhance system reliability. Power ORing diodes are com-

monlyusedtoconnectthesesuppliesatthepointofloadat

the expense of power loss due to significant diode forward

voltage drop. The LTC4236 minimizes this power loss by

using external N-channel MOSFETs as the pass elements,

allowing for a low voltage drop from the supply to the load

when the MOSFETs are turned on. When an input source

voltage drops below the output common supply voltage,

the appropriate MOSFET is turned off, thereby matching

the function and performance of an ideal diode. By adding

a current sense resistor and a Hot Swap MOSFET after

the parallel-connected ideal diode MOSFETs, the LTC4236

enhances the ideal diode performance with inrush current

limiting and overcurrent protection (see Figure 1). This

allows the board to be safely inserted and removed from

a live backplane without damaging the connector.

applicaTions inForMaTion

Internal VCC Supply

The LTC4236 operates with an input supply from 2.9V to

18V. The power supply to the device is internally regulated

at 5V by a low dropout regulator (LDO) with an output at

the INTVCC pin. An internal diode-OR circuit selects the

highest of the supplies at the IN and OUT pins to power the

devicethroughtheLDO.Thediode-ORschemepermitsthe

device’s power to be kept alive by the OUT voltage when

the IN supplies have collapsed or shut off.

AnundervoltagelockoutcircuitpreventsalloftheMOSFETs

from turning on until the INTVCC voltage exceeds 2.2V. A

0.1µF capacitor is recommended between the INTVCC and

GND pins, close to the device for bypassing. No external

supply should be connected at the INTVCC pin so as not

to affect the LDO’s operation. A small external load of less

than 500µA can be connected at the INTVCC pin.

Figure 1. Card Resident Diode-OR with Hot Swap Application

ADC

CPO1

GND

FAULT

PWRGD

DSTAT1

DSTAT2

680µF

12V

INTVCC

SMAJ15A

D2OFF

IN1 DGATE1

DGATE2

4236 F01

MD2

SiR158DP

0.003

HGATE OUT

SENSE+ CS+

SENSE–

D2SRC

CPO2

0.1µF

IN2

13.7k

15k

RHG

CHG

10nF

REG

0.1µF

MD1

SiR158DP

SMAJ15A

DTMR

CFT

0.1µF

CDT

0.1µF

FTMR

IMON

0.1µF

LTC4236

BACKPLANE

CONNECTOR

VIN1

12V

VIN2

12V

CARD

CONNECTOR

VSENSE+

100k

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