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ADM1070
–48 V Hot Swap Controller
FUNCTIONAL BLOCK DIAGRAM
V
CC
AND
REFERENCE
GENERATOR
OVER-UNDER
VOLTAGE DETECTION
CIRCUIT
FAULT TIMER AND
CONTROL
OSCILLATOR
SENSE
0V
V
DD
R1
R2
–48V
V
EE
UV/OV
TIMER
R
DROP
12V
16k⍀
V
IN
V
CC
V
REF
EN
100mV
V
IN
45A
GATE
V
EE
R
SENSE
C
LOAD
V
OUT
()*
*OPTIONAL TIMER CAPACITOR
ADM1070
Q1
FEATURES
Allows Safe Board Insertion and Removal from a Live
–48 V Backplane
Typically Operates from –36 V to –80 V
Tolerates Transients up to –200 V (Limited by External
Components)
Accurate Programmable Linear Current Limit for
In-Rush Control and Short Circuit Protection
Programmable Timeout in Current Limit
Limited Consecutive Retry:
Auto-Restart after Current Limit Timeout
Shutdown after Seven Consecutive Auto Restarts
Provides Immunity from Step Induced Current Spikes
Default Timing Provided with no TIMER Capacitor
Single Pin Undervoltage/Overvoltage Detection
Programmable Operating Voltage Window
Programmable Undervoltage/Overvoltage Time Filter
Small 6-Lead SOT-23 Package
APPLICATIONS
Central Office Switching
–48 V Distributed Power Systems
Negative Power Supply Control
Hot Board Insertion
Electronic Circuit Breaker
High Availability Servers
Programmable Current Limiting Circuit
–48 V Power Supply Modules
GENERAL DESCRIPTION
The ADM1070 is a negative voltage hot swap controller that
allows a board to be safely inserted and removed from a live
–48 V backplane. The part achieves this by providing robust
current limiting, protection against transient and nontransient
short circuits and overvoltage and undervoltage conditions. The
ADM1070 typically operates from a negative voltage of up to
–80 V and can tolerate transient voltages of up to –200 V.
In-rush current is limited to a programmable value by control-
ling the gate drive of an external N-channel FET. The current
limit can be controlled by the choice of the sense resistor,
R
SENSE
. Added control of the in-rush current is provided by an
on-chip timer that uses pulsewidth modulation to allow the
maximum current to flow for only 3% of the time. An autorestart
occurs after a current limit timeout. After seven successive
autorestarts, the fault will be latched and the part goes into
shutdown with the result that the external FET is disabled until
the power is reset.
The ADM1070 also features single-pin undervoltage and over-
voltage detection. The FET is turned off if a nontransient
voltage less than the undervoltage threshold, typically –36 V, or
greater than the overvoltage threshold, typically –77 V, is detected
on the UV/OV Pin. The operating voltage window of the
ADM1070 is programmable and is determined by the ratio R1/R2.
Time filtering on the undervoltage and overvoltage detection
and current limiting is programmable via the TIMER Pin. An
external capacitor connected between the TIMER Pin and V
EE
determines the undervoltage/overvoltage time filter and the
timeout in current limit. If the pin is tied to V
EE
, the time filter
values and the current limit timeout revert to default figures.
The ADM1070 is fabricated using BiCMOS technology for mini-
mal power consumption. The part is available in a small
6-Lead SOT-23 package.
