LTC4216 Datasheet, PDF (21/24 Pages) Linear Technology – Ultralow Voltage Hot Swap Controller

LTC4216
APPLICATIO S I FOR ATIO
BACKPLANE PCB EDGE
CONNECTOR CONNECTOR
(FEMALE)
(MALE)
V_CC
5V
V_IN
3.3V
ON/RST
ON/OFF
GND
LONG
LONG
Z1
C_Y
330nF
R_Y
22Ω
R_SENSE
0.004Ω
M1
Si4864DY
R8
10k
R_X
10Ω
C_X
100nF
R5
39.2k
1%
+ _CLOAD
1000µF
V_OUT
3.3V
5A
SHORT
SHORT
R3
20k 1%
SHORT
M2
R2
4.42k
1%
R1
M3 5.62k
1%
LONG ^{PCB CONNECTION SENSING}
11 10
9
8
2
V_CC SENSEP SENSEN GATE
7
R7
ON
LTC4216
FB
R4
10k
1%
10k
R6
10k
12
FAULT
TIMER SS FILTER GND RESET ¹
4
5
3
6
C1
C2
C3
10nF 4.7nF 33nF
Z1: SMAJ6.0A
M2, M3: 2N7002K
µP
LOGIC
FAULT
RESET
4216 F16
Figure 16. PCB Connection Sensing with ON/OFF Control
BACKPLANE PCB EDGE
CONNECTOR CONNECTOR
(FEMALE) (MALE)
V_IN
LONG
5V
Z1 ^RX
10Ω
C_X
R_Y R_SENSE
22Ω 0.004Ω
C_Y
330nF
M1
Si4864DY
R_Z
100Ω
C_Z
10nF
R4
64.9k
1%
+
C_LOAD
470µF
V_OUT
5V
5A
SHORT
100nF
R2
80.6k
1%
11 10
9
8
V_CC SENSEP SENSEN GATE
2
ON
LTC4216
7
R6
FB
R3
10k
1%
10k
R5
10k
µP
LOGIC
R1
20k
1% TIMER
SS
FILTER
FAULT ¹²
GND RESET ¹
FAULT
RESET
4
5
3
6
C1
C2
C3
GND
LONG
10nF 4.7nF 22nF
Z1: SMAJ6.0A
4216 F17
Figure 17. 5V Hot Swap Application
⎯R⎯E⎯S⎯E⎯T high when V_OUT rises above 4.5V. Transient volt-
age suppressor, Z1, and snubber network, R_X and C_X,
connected at SENSEP pin are highly recommended to
protect the 5V supply system from ringing and voltage
spikes during a fault condition. The RC network, R_Y and
C_Y, connected at the V_CC pin, allows the LTC4216 bias
supply to ride out supply glitches during a fault condition
or adjacent board shorts.
Auto-Retry after a Fault
As shown in Figure 18, the LTC4216 can be configured to
automatically retry after a fault condition by connecting
both the ^⎯F^⎯A^⎯U^⎯L^⎯T and ON pins together with an RC network.
The network has a pull-up resistor, R_AUTO, tied to the load
supply (V_IN) and an external capacitor, C_AUTO, connected
to ground. The auto-retry circuit will attempt to restart
the LTC4216 after a circuit breaker trip, as shown in the
timing diagram of Figure 19. In addition to the cooling
cycle provided by the TIMER period during auto-retry
sequence, the RC time constant for the ON pin voltage to
reach 0.8V provides additional turn-off time to prevent
the external MOSFET from overheating. The auto-retry
duty cycle is given by:
Duty Cycle ≈ ^{tSS + tFILTER •100%}
t_OFF + t_TIMER + t_SS + t_FILTER
(20)
where
t_TIMER = TIMER period as given by Equation (1);
t_OFF = time taken to charge the capacitor, C_AUTO, from
⎯F⎯A⎯U⎯L⎯T V_OL to V_ON(TH) threshold (0.8V). As there is an
internal 5µA current source pull-up at the ^⎯F^⎯A^⎯U^⎯L^⎯T pin, it
4216f
21