LTC1647 LINER [Linear Technology], LTC1647 Datasheet - Page 11

• Manufacturer Part Number: LTC1647
• Description: Hot Swap Controller
• Manufacturer: LINER [Linear Technology]

clamps at the GATE pin determine the gate drive voltage
(ΔV
minimum 4.5V of ΔV
≤ V
by zener clamp Z1 connected between the GATE and V
pins. The ΔV
minimum value of 10V. For V
Z2 begins to set the limitation for ΔV
gate voltage to ground to 26V typically. The minimum Z2’s
clamp voltage is 23V. This effectively sets ΔV
minimum at V
SENSE (Pin 7/Pin 8): Circuit Breaker Set Pin. With a sense
resistor placed in the power path between V
the LTC4211’s electronic circuit breaker trips if the voltage
across the sense resistor exceeds the thresholds set inter-
nally for the SLOW COMP and the FAST COMP, as shown
in the Block Diagram. The threshold for the SLOW COMP is
V
if the voltage across the sense resistor exceeds 50mV for
20μs. The SLOW COMP delay is fixed in the S8/MS8 ver-
sion and adjustable in the MS version of the LTC4211. To
adjust the SLOW COMP’s delay, please refer to the section
on Adjusting SLOW COMP’s Response Time.
Under transient conditions where large step current
changes can and do occur over shorter periods of time,
a second (fast) comparator instead trips the electronic
circuit breaker. The threshold for the FAST COMP is set at
V
voltage across the sense resistor exceeds 150mV for
more than 300ns. The FAST COMP’s delay is fixed in the
LTC4211 and cannot be adjusted. To disable the electronic
circuit breaker, connect the V
PIN FUNCTIONS
CB(SLOW)
CB(FAST)
CC
GATE
< 4.75V. For 4.75V ≤ V
= V
= 150mV, and the circuit breaker trips if the
= 50mV, and the electronic circuit breaker trips
GATE
GATE
CC
= 15V.
– V
is typically at 12V and with guaranteed
GATE
CC
). The charge pump produces a
for supplies in the range of 2.7V
CC
(8-Lead Package/10-Lead Package)
CC
CC
≤ 12V the ΔV
and SENSE pins together.
> 12V, the Zener clamp
GATE
. Z2 clamps the
CC
GATE
and SENSE,
GATE
is limited
to 8V
CC
V
the LTC4211. The LTC4211 operates from 2.5V < V
16.5V, and the supply current is typically 1mA. An internal
undervoltage lockout circuit disables the device until the
voltage at V
FAULT (Not available on S8/MS8, Pin 10 MS): FAULT is
both an input and an output. Connected to this pin are an
analog comparator (COMP6) and an open-drain N-channel
FET. During normal operation, if COMP6 is driven below
1.236V, the electronic circuit breaker trips and the GATE
pin pulls low. Typically, a 10k pull-up resistor connects
to the FAULT pin. This pull-up is required to allow the
LTC4211 to begin a second timing cycle (V
and start-up properly. This also allows the use of the
FAULT pin as a status output. Under normal operating
conditions, the FAULT output is a logic high. Two condi-
tions cause an active low on FAULT: (1) the LTC4211’s
electronic circuit breaker trips because of an output short
circuit causing a fast output overcurrent transient (FAST
COMP trips circuit breaker); or (2) V
FAULT output is driven to logic low and is latched logic
low until the ON pin is driven to logic low for 150μs (the
t
FILTER (Not available S8/MS8, Pin 3 MS): Overcurrent
Fault Timing Pin and Overvoltage Fault Set pin. With a
capacitor connected from this pin to ground, the SLOW
COMP’s response time can be adjusted. In the S8/MS8
version of the LTC4211, the FILTER pin is not available
and the delay time from overcurrent detect to GATE OFF
is fixed at 20μs.
RESET
CC
(Pin 8/Pin 9): This is the positive supply input to
duration).
CC
exceeds 2.3V.
FILTER
LTC4211
> 1.236V. The
FAULT
> 1.286)
11
CC
4211fb
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