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LTC4371

4371f

For more information www.linear.com/LTC4371

applicaTions inForMaTion

Figure 18. –36V to –72V/25A Ideal Diode-OR

As a second design example, consider modifying the

circuit of Figure 17 to handle 300V transients and to drive

a red LED, which illuminates when a fault is present (see

Figure 18). RDA and RDB are sized to handle transients to

300V, so no change in their value is necessary. Modifica-

tions are necessary to drive the red LED.

A PZTA42, a 300V NPN with a minimum β = 20 is chosen

to supply both the LED and the VDD pin. With a maxi-

mum IDD of 9.5mA (LTC4371) + 1mA (LED) = 10.5mA,

Equation 4 gives:

IBASE =

10.5mA

= 525µA

(13)

RZ <

36V –11.8V

50uA+

10mA

= 44k

The nearest lower 5% value is 43k.

To produce 1mA LED current with variations in the circuit,

R1 is chosen to be 8.2k.

4371 F18

LTC4371

GA GB

VDD

SB VSS

RDA

20k

RDB

20k

IPT020N10N3

–36V TO

–72V

–36V TO

–72V

VOUT

25A LOAD

RED LED = MOSFET BAD

43k

8.2k

RTN

FAULTB

PZTA42

0.1F

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