Full-Feature −48 V Hot Swap Controller
Data Sheet
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FEATURES
Precision inrush linear current limit
Soft start inrush current limit profiling
Precision maximum on-time in current limit
Maximum on-time modulated by FET drain voltage for
additional SOA protection
Adjustable PWM retry scheme and multiple device cascading
capability for charging large capacitive loads
Limited number of PWM cycles for FET SOA protection under
short circuit condition
Ability to configure device as continuous autoretry with a
5-second cooling period
Shunt regulator topology to allow very large transient input
supplies
Separate UV and OV pins for programming allowable input
supply window
Programmable OV hysteresis using current source into pin
when supply is high
Programmable UV hysteresis using current sink from pin
when supply is low
PWRGD
output indicates when capacitor charging complete
SPLYGD
output indicates when supply is within
valid window
LATCHED
output indicates the end of the retry cycle before
load capacitance is charged
SHDN
input for user-commanded shutdown
RESTART
input for user-triggered 5-second shutdown and
autorestart— virtual card reseat
FUNCTIONAL BLOCK DIAGRAM
04488-001
FAULT TIMER
AND CONTROL
OSCILLATOR
PWM
TIMEOUT
FOLDBACK
AND PWRGD
5 SECOND
SHUTDOWN
t
ON
CONTROL
SOFT START
CONTROL
UNDERVOLTAGE
DETECTOR
OVERVOLTAGE
DETECTOR
V
CC
AND
REFERENCE
GENERATOR
LATCHEDRESTART
SPLYGDV
IN
OV
UV
SS
TIMER
SHDN
V
EE
SENSE
GATE
DRAIN
PWRGD
100mV(MAX)
50∝A
V
IN
Figure 1.
APPLICATIONS
Central office switching
Telecommunication and data communication equipment
−48 V distributed power systems
Negative power supply control
High availability servers
−48 V power supply modules
Disk arrays
GENERAL DESCRIPTION
The ADM1073 is a full-feature, negative voltage, hot swap
controller that allows boards to be safely inserted and removed
from a live −48 V backplane. The part provides precise and
robust current limiting, and protection against both transient
and nontransient short circuits in overvoltage and undervoltage
conditions. The ADM1073 can operate from a negative voltage
of −18 V to −80 V and can tolerate transient voltages of up to
−200 V.
Inrush current is limited to a programmable value by control-
ling the gate drive of an external N-channel FET. The maximum
current limit is set by the choice of the sense resistor, R
SENSE
.
A built-in soft start function allows control of the inrush
current profile by an external capacitor on the soft start (SS)
pin.
An external capacitor on the TIMER pin determines the time
for which the FET gate is controlled to be high when maximum
inrush current flows. The ADM1073 employs a limited consec-
utive retry scheme, whereby, if the load capacitance is not fully
charged within one attempt, the FET gate is pulled low and
retries after a cooling period.
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