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LTC4223-1/LTC4223-2

422312f

APPLICATIONS INFORMATION

Supply Transient Protection

The supply inputs, AUXIN and 12VIN are fed directly from

the regulated output of the backplane supply, where bulk

bypassing assures a spike-free operating environment.

In other applications where the bulk bypassing is located

far from the LTC4223, spikes generated during output

short circuit events could exceed the absolute maximum

ratings for AUXIN and 12VIN. To minimize such spikes,

use wider traces or heavier trace plating to reduce the

power trace inductance. Also, bypass locally with a 10μF

electrolytic and 100nF ceramic, or alternatively clamp

the input with a transient voltage suppressor (Z1, Z2) as

shown in Figure 13. A 10Ω, 100nF snubber damps the

response and eliminates ringing. A recommended layout

of the 12V transient protection devices Z1, R1 and C1

around the LTC4223 is shown in Figure 12.

Figure 9. Auto-Retry after 12V Overcurrent Fault

FAULT

TIMER

12VGATE

12VOUT

VTMR

422312 F08

12VIN - 12VSENSE

200

μA

60mV

4 5

μA

FAULT PULLS LOW DUE TO

12V OVERCURRENT FAULT

START OF COOL-OFF CYCLE

START OF

DEBOUNCE CYCLE

RESET FAULT HIGH

FAULT PULLS LOW AND

RESTART OF COOL-OFF CYCLE

END OF DEBOUNCE CYCLE

START 12V GATE RAMP WHEN STARTUP CONDITIONS ARE MET

12V OUTPUT IN CURRENT LIMIT

RESTART OF

DEBOUNCE CYCLE

COOL-OFF CYCLE

DEBOUNCE CYCLE

FILTER DELAY

COOL-OFF CYCLE

μA2μA

μA

200

μA10μA

12VGATE REGULATES

422312 F10

12VSENSE

VSENSE

–

LTC4223

12VIN

12VGATE

VOUT

12IMON

ILOAD

RIN

12V

TO SYSTEM

CONTROLLER

μF

3.3V

LTC1197L

VREF

CLK

DOUT

+IN

–IN

VCC

GND

ROUT

165k

VOUT =

• VSENSE = 33 • VSENSE

ROUT

RIN

LOAD

Figure 10. High Side Current Sense with LTC1197L ADC

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