ADM1281

RECOMMENDED FOR NEW DESIGNS

Hot-Swap Controller and Digital Power and Energy Monitor with PMBus Interface

Data Sheet (Rev. A) Product Selection Table
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Overview

  • Drop-in replacement to ADM1278
  • ±0.3% accurate, 12-bit ADC for IOUT, VIN, VOUT, and temperature
  • 290 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
  • Reports power and energy consumption over time
  • Peak detect registers for current, voltage, and power
  • PROCHOT power throttling capability
  • PMBus fast mode compliant interface
  • Available in 5 mm × 5 mm, 32-lead LFCSP package

The ADM1281 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 through 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 through the HS+ and HS− pins. A default current limit of 20 mV is set, but this limit can be adjusted, if required.

The ADM1281 limits the current through the sense resistor by controlling the gate voltage of an external N-channel FET in the power path, through the GATE pin. The sense voltage, and therefore the load current, is maintained below the preset maximum. The ADM1281 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.

In case of a short-circuit event, a fast internal overcurrent detector responds within 290 ns and signals the gate to shut down. A 2400 mA pull-down device ensures a fast FET response.

The ADM1281 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 ADM1281 is available in a 32-lead LFCSP with a RETRY pin that can be configured for automatic retry or latch-off when an overcurrent fault occurs.

APPLICATIONS

  • Servers
  • Power monitoring and control/power budgeting
  • Telecommunication and data communication equipment
ADM1281
Hot-Swap Controller and Digital Power and Energy Monitor with PMBus Interface
ADM1281 Typical Application Circuit ADM1281 Pin Configuration ADM1281 Pin Configuration ADM1281 Pin Configuration
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Documentation

Data Sheet 1

User Guide 2

Application Note 1

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Software Resources

Device Drivers 1

Tools & Simulations

LTpowerPlay®

LTpowerPlay® is a powerful, Windows-based development environment supporting Linear Technology's Digital Power System Management (PSM) products.

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Design Tool 1

Evaluation Kits

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EVAL-ADM1281-AZ

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Features and Benefits

  • Fully functional evaluation board for the ADM1281
  • Populated and tested with 12 V, 73 A, and 3 mF design
  • Special N-MOSFET footprint suits different packages
  • Supports up to five sense resistors in parallel
  • Supports up to six FETs in parallel
  • LED indicated status outputs
  • Wide input-voltage range of up to 20 V
  • FET temperature measurement capability
  • Supports cascade setup for multiple boards
  • Toggle and push-button switch for easy input control
  • PMBus communication supported

Product Details

The EVAL-ADM1281-AZ is a compact, full-featured evaluation board for the ADM1281. The board layout provides a clear visual of all the peripheral components and the hot-swap power path. The layout also maximizes the ability of the board to dissipate heat for some of the key components on the power path, which allows the evaluation of very high current hot-swap setups.

Five sense-resistor slots and six multipackage FET slots provide great flexibility and allow a wide range of application setups.

Multiple test points allow easy access to all critical points/pins. Seven LEDs provide direct visual indication on variations in the board status, such as supply input, output, IC power-good output, fault output, current sense output, and general-purpose outputs (GPO). An AD7291 8-channel, I2C, 12-bit, successive approximation analog-to-digital converter (SAR ADC) allows users to measure voltages such as CSOUT and other pin voltages, as well as to read ambient board temperature through an I2C bus in real time.

The evaluation board supports I2C communication, which allows users to communicate with the ADM1281. The evaluation board also supports cascade setup so multiple evaluation boards can be connected together and share the same I2C bus.

The boards are fully compatible with the hot-swap and power monitoring evaluation software and the LTpowerPlay tools, which can be downloaded from the ADM1281 product page.

Users need a USB-SDP-CABLEZ or a DC1613A USB-to-I2C serial interface to use the evaluation software tools.

The standard evaluation board is prepopulated and tested with a 12 V, 73 A hot-swap design, which is capable of working with a 3 mF output capacitor.

mF output capacitor. Full specifications on the ADM1281 are available in the ADM1281 data sheet available from Analog Devices, Inc., and must be consulted with this user guide when using the EVAL-ADM1281-AZ evaluation board.
EVAL-ADM1281-AZ
EVAL-ADM1281-AZ - Angle view EVAL-ADM1281-AZ - Bottom view EVAL-ADM1281-AZ - Top view

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