Datasheet

LTC4216
23
4216fa
For more information www.linear.com/LTC4216
FAULT V
OL
to V
ON(TH)
threshold (0.8V). As there is an
internal 5µA current source pull-up at the FAULT pin, it
complicates the equation for t
OFF
. This is approximately
given by:
t
RC VV
VV
RA
OFF
AUTOAUTOONT
HO
L
IN ON TH AUTO
≈
−
+µ
••()
(–
)•
()
()
5
(21)
t
FILTER
= circuit breaker response time as given by Equation
(2); t
SS
= approximated time taken to charge the soft-start
capacitor, C2, from 0V to its final value (1.65V) by 10µA
current source only.
For the component values shown, the external RC time
constant is set at 0.2 second, t
TIMER
= 62ms, t
OFF
= 25ms
at V
IN
= 5V, t
SS
= 1.6ms, t
FILTER
= 480µs and the auto-retry
duty cycle is 2.3%. The auto-retry duty cycle can be further
reduced by increasing both the t
TIMER
delay and the RC
delay. As an example, increasing the TIMER capacitor, C1,
value from 100nF to 330nF, and R
AUTO
value from 200k
to 470k reduces the duty cycle to 0.8%.
Figure 19. Auto-Retry Timing
Figure 18. Auto-Retry Application
SENSEP SENSEN
GATE
ON
FB
SS
11 10 9 8
7
12
1
4
2
5 36
FILTER
LTC4216
R3
10k
1%
R4
64.9k
1%
C
Y
330nF
C
X
100nF
R
AUTO
200k
C
AUTO
1µF
R5
10k
LONG
SHORT
LONG
BACKPLANE
CONNECTOR
(FEMALE)
PCB EDGE
CONNECTOR
(MALE)
GND
C1
100nF
C2
4.7nF
C3
22nF
V
IN
5V
V
OUT
5V
5A
GND
M1
Si4864DY
+
C
LOAD
470µF
V
CC
Z1: SMAJ6.0A
TIMER
Z1
FAULT
RESET
RESET
4216 F18
R
SENSE
0.004Ω
R
Y
22Ω
R
X
10Ω
TIMER
SENSEP–SENSEN
SENSEP
FILTER
SS
2.4µA
V
TMR(TH)
V
FILT(TH)
2µA
V
TMR(TH)
2µA
40mV
25mV
10µA
10µA
1µA
1
2 3 4 6 7 8 9
0.4V
0.8V
V
OL
10 11 12 13 145
CHECK FOR GATE, FILTER,
TIMER, SS < 0.2V
CHECK FOR GATE, FILTER,
TIMER, SS < 0.2V AND FAULT HIGH
FAULT PULLED LOW
4216 F19
ON/FAULT
0.8V
ELECTRONIC CIRCUIT
BREAKER ARMED
OUTPUT IN ANALOG CURRENT LIMIT
ON/
DEVICE RESET
1ST TIMING CYCLE RESTART
FILTER RAMPS UP WHEN
(V
SENSEP
–V
SENSEN
) >25mV
GATE
(V
GATE
– V
OUT
) > V
GS(TH)
TRACKS SS RAMP
GATE
REGULATING
60µA
t
FILTER
t
SS
t
OFF
t
TIMER
t
RST(ONLO)
t
OFF
t
TIMER
applicaTions inForMaTion