LTC4413 datasheet(24/32 Pages) AD

24 / 32 page

LTC4421

Rev. 0

For more information www.analog.com

APPLICATIONS INFORMATION

master LTC4421 to CASIN of the lower priority slave

LTC4421, as shown in Figure 13.

When both master input supplies are invalid, the master

verifies that it has disconnected both supplies from the

output before driving its CASOUT pin high. This ensures

the reverse conduction paths from the output back to the

master inputs are blocked before the slave is allowed to

power the output. The master LTC4421 pulls CASOUT

up to INTVCC using a 20µA current source, allowing the

slave LTC4421 to connect its highest priority valid supply

to the output.

When the slave is powering the output and one of the

master’s inputs becomes valid, the master simultane-

ously connects its valid channel to the output and drives

its CASOUT pin low to force the slave to disconnect its

inputs. To prevent cross conduction, make the connection

between the master’s CASOUT and slave’s CASIN as short

as possible. This minimizes the capacitance of the con-

nection and hence the turn-off delay of the slave channel.

This scheme can be extended to prioritize as many input

supplies as necessary. Connect each additional lower

priority LTC4421’s OUT pins to the common output volt-

age and connect its CASIN pin to the CASOUT pin of the

next higher priority LTC4421. Note that driving the mas-

ter LTC4421’s CASIN pin low disconnects all input sup-

plies in the system. Driving the master’s DISABLE1 and

DISABLE2 pins low disconnects the master’s inputs from

the output and allows the slave LTC4421’s to connect to

the output.

Figure 13. Using Two LTC4421’s in a Cascading Application to Prioritize Four Input

Supplies. (The Master and Slave V2 Power Paths are Omitted for Clarity)

CG1

SiR158DP

2.5m

RSENSE1

47nF

GATE1 SOURCE1

CASIN

CASOUT

SENSE1

OUT1

DISABLE1

DISABLE2

SiR158DP

2.5m

RSENSE3

CG3

47nF

CASIN

SHDN

CASOUT

VOUT

LTC4421

MASTER

LTC4421

LTC4421 F13

SLAVE

L = DISCONNECT ALL CHANNELS

H = CONNECT HIGHEST PRIORITY VALID CHANNEL

L = DISABLE MASTER, ENABLE SLAVE

CONNECT HIGH

GATE1 SOURCE1

SENSE1

OUT1

LTC4413 Datasheet(PDF) 24 Page - Analog Devices

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