Datasheet

LTC4223-1/LTC4223-2
17
422312f
APPLICATIONS INFORMATION
Supply Transient Protection
The supply inputs, AUXIN and 12V
IN
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 12V
IN
. 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
12V
GATE
12V
OUT
V
TMR
V
TMR
V
TMR
422312 F08
12V
IN
- 12V
SENSE
200μA
60mV 60mV
12345678
2μA
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
2μA2μA10μA 200μA10μA
12V
GATE
REGULATES
422312 F10
12V
SENSE
V
SENSE
– +Q1
LTC4223
12V
IN
12V
GATE
V
OUT
12IMON
I
LOAD
R
IN
5k
12V
TO SYSTEM
CONTROLLER
CS
1μF 3.3V
LTC1197L
V
REF
CLK
D
OUT
+IN
–IN
V
CC
GND
–
+
R
OUT
165k
V
OUT
= • V
SENSE
= 33 • V
SENSE
R
OUT
R
IN
LOAD
Figure 10. High Side Current Sense with LTC1197L ADC