Full-Feature −48 V Hot Swap Controller
ADM1073
FEATURES
FUNCTIONAL BLOCK DIAGRAM
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
V
SPLYGD
IN
PWRGD
DRAIN
V
AND
CC
REFERENCE
FOLDBACK
AND PWRGD
GENERATOR
OVERVOLTAGE
DETECTOR
OV
UV
V
IN
UNDERVOLTAGE
DETECTOR
50µA
100mV(MAX)
GATE
SOFT START
CONTROL
SS
SENSE
tON CONTROL
TIMER
FAULT TIMER
AND CONTROL
V
EE
Separate UV and OV pins for programming allowable input
supply window
5 SECOND
SHUTDOWN
PWM
TIMEOUT
OSCILLATOR
Programmable OV hysteresis using current source into pin
when supply is high
SHDN
RESTART
LATCHED
Programmable UV hysteresis using current sink from pin
when supply is low
Figure 1.
PWRGD output indicates when capacitor charging complete
APPLICATIONS
SPLYGD output indicates when supply is within
valid window
LATCHED output indicates the end of the retry cycle before
load capacitance is charged
Central office switching
Telecommunication and data communication equipment
−48 V distributed power systems
Negative power supply control
High availability servers
SHDN input for user-commanded shutdown
RESTART input for user-triggered 5-second shutdown and
autorestart— virtual card reseat
−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.
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.
Inrush current is limited to a programmable value by control-
ling the gate drive of an external N-channel FET. The maximum
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current limit is set by the choice of the sense resistor, RSENSE
.
Rev. 0
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