Hot Swap Controller and Digital Power and
Energy Monitor with PMBus Interface
ADM1278
Data Sheet
FEATURES
TYPICAL APPLICATION CIRCUIT
RSENSE
Q
4.5V TO 20V
1
0.3% accurate, 12-bit ADC for IOUT, VIN, VOUT, and temperature
320 ns response time to short circuit
Shutdown on detection of FET health fault
Constant power foldback for tighter FET SOA protection
Remote temperature sensing with programmable warning
and shutdown thresholds
Resistor-programmable 5 mV to 25 mV VSENSE current limit
Programmable start-up current limit
1% accurate UV, OV, and PWRGD thresholds
Split hot swap and power monitor inputs to allow additional
external ADC filtering
HS+
MO+
MO– HS–
VCC
VCAP
UV
ADM1278-1
–
+
×50
CHARGE
PUMP
LDO
ISENSE
VCP
+
–
GATE
DRIVE/
LOGIC
1.0V
1.0V
GATE
TEMP
OV
–
+
TIMEOUT
+
–
PWGIN
ISET
REF
SELECT
+
–
PSET
1.0V
1.0V
CURRENT-
LIMIT
CONTROL
ISTART
HS–
VOUT
Reports power and energy consumption over time
Peak detect registers for current, voltage, and power
PROCHOT power throttling capability
PMBus fast mode compliant interface
5 mm × 5 mm, 32-lead LFCSP
VCBOS
PWRGD
FAULT
ENABLE
GPO2/ALERT2
GPO1/ALERT1/CONV
SCL
SDA
ADR1
ADR2
IOUT
TIMER
TIMER
TIMEOUT
LOGIC
AND
HS+
ISENSE
12-BIT
ADC
PMBus
V
OUT
TEMP
RETRY
APPLICATIONS
ANALOG
VOUT
CSOUT
Servers
Power monitoring and control/power budgeting
Telecommunication and data communication equipment
PGND
GND
Figure 1.
GENERAL DESCRIPTION
The ADM1278 is a hot swap controller that allows a circuit board
to be removed from or inserted into a live backplane. It also features
current, voltage, power, and temperature readback via an integrated
12-bit analog-to-digital converter (ADC), accessed using a PMBus™
interface. The load current is measured using an internal current
sense amplifier that measures the voltage across a sense resistor
in the power path via the HS+ and HS− pins. A default current
limit of 20 mV is set, but this limit can be adjusted, if required.
In case of a short-circuit event, a fast internal overcurrent
detector responds within 320 ns and signals the gate to shut
down. A 1500 mA pull-down device ensures a fast FET response.
The ADM1278 features overvoltage (OV) and undervoltage (UV)
protection, programmed using external resistor dividers on the
UV and OV pins. A PWRGD signal can be used to detect when
the output supply is valid, using the PWGIN pin to accurately
monitor the output.
The ADM1278 limits the current through the sense resistor by
controlling the gate voltage of an external N-channel FET in the
power path, via the GATE pin. The sense voltage, and therefore
the load current, is maintained below the preset maximum. The
ADM1278 protects the external FET by limiting the time that
the FET remains on while the current is at its maximum value.
This current-limit time is set by the choice of capacitor connected
to the TIMER pin. In addition, a constant power foldback scheme
is used to control the power dissipation in the MOSFET during
power-up and fault conditions. The level of this power, along
with the TIMER regulation time, can be set to ensure that the
MOSFET remains within safe operating area (SOA) limits.
RETRY
The ADM1278 is available in a 32-lead LFCSP with a
pin
that can be configured for automatic retry or latch-off when an
overcurrent fault occurs.
Table 1. Model Options
Model
ADC Accuracy SPI Interface Enable Pin1
ADM1278-1AA
ADM1278-1A
ADM1278-1B
ADM1278-2A
ADM1278-3A
0.3%
0.7%
1.0%
0.7%
0.7%
No
No
No
Yes
No
Active high
Active high
Active high
Active high
Active low
1
ENABLE
Active high relates to the ENABLE pin, and active low relates to the
pin.
Rev. A
Document Feedback
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responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rightsof third parties that may result fromits 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 andregisteredtrademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
Technical Support
©2014 Analog Devices, Inc. All rights reserved.
www.analog.com
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