Hot Swap Controller and
Digital Power Monitor with AlertB Output
Preliminary Technical Data
ADM1178
FEATURES
FUNCTIONAL BLOCK DIAGRAM
Allows Safe Board Insertion and Removal from a Live
Backplane
Controls Supply Voltages from 3.15 V to14 V
Precision Current Sense Amplifier
ADM1178
Mux
V
I
VCC
0
1
SDA
SCL
ADR
12-Bit
ADC
+
A
-
I2C
Precision Voltage Input
SENSE
12-Bit ADC for Current and Voltage Readback
Charge Pumped Gate Drive for External N-FET Switch
Adjustable Analog Current Limit with Circuit Breaker
Fast Response Limits Peak Fault Current
Automatic Retry or Latch-Off On Current Fault
Programmable hot swap timing via TIMER pin
Active-high ON pin
Current Sense
Amplifier
Alert
ALERTB
GATE
FET Drive
Controller
+
ON
-
1.3V
UV Comparator
AlertB pin for overcurrent interrupt
I2C Fast Mode compliant interface (400 KHz max)
10-lead MSOP package
TIMER
GND
Figure 1.
APPLICATIONS DIAGRAM
APPLICATIONS
Power Monitoring/Power Budgeting
Central office Equipment
RSENSE
N-Channel FET
3.15V - 14V
Telecommunication and Datacommunication Equipment
PC/Servers
SENSE
Vcc
CONTROLLER
GATE
ADM1178
GENERAL DESCRIPTION
SDA
SCL
SDA
SCL
ON
P=VI
The ADM1178 is an integrated hotswap controller and current
sense amplifier that offers digital current and voltage
monitoring via an on-chip 12-bit ADC, communicated through
an I2C interface.
TIMER
ALERTB
ADR
INTERRUPT
GND
Figure 2.
An internal current sense amplifier senses voltage across the
sense resistor in the power path via the VCC and SENSE pins.
A 12-bit ADC can measure the current seen in the sense
resistor, and also the supply voltage on the VCC pin.
The ADM1178 limits the current through this resistor by
controlling the gate voltage of an external N-channel FET in the
power path, via the GATE pin. The sense voltage (and hence the
inrush current) is kept below a preset maximum.
An industry standard I2C interface allows a controller to read
current and voltage data from the ADC. Measurements can be
initiated by an I2C command. Alternatively the ADC can run
continuously and the user can read the latest conversion data
whenever it is required. Up to 4 unique I2C addresses can be
created by the way the ADR pin is connected.
The ADM1178 protects the external FET by limiting the time
that it spends with the maximum current running in it. This
current limit period is set by the choice of capacitor attached to
the TIMER pin. Additionally, the device provides protection
from overcurrent events at times after the hot-swap event is
complete. In the case of a short-circuit event the current in the
sense resistor will exceed an overcurrent trip threshold, and the
FET will be switched off immediately by pulling down the
GATE pin.
The ADM1178 is packaged in a 10-lead MSOP package.
Rev. PrD May 2006
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarks and registeredtrademarks arethe property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
Fax: 781.461.3113
www.analog.com
© 2006 Analog Devices, Inc. All rights reserved.
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