Hot Swap Controller and Digital Power and Energy Monitoring with PMBus Interface Data Sheet ADM1276 FEATURES FUNCTIONAL BLOCK DIAGRAM SENSE+ SENSE Controls supply voltages from 2 V to 20 V + ADM1276-3 VCC 50 370 ns response time to short circuit CHARGE VCAP LDO PUMP Resistor-programmable 5 mV to 25 mV current limit IOUT ENABLE V CP 1% accurate, 12-bit ADC for current, V /V readback UV IN OUT + GATE 1.0V DRIVE/ Charge pumped gate drive for multiple external N-channel FETs GATE LOGIC OV VOUT + High gate drive voltage to ensure lowest R 1.0V TIMEOUT DSON + CURRENT Foldback for tighter FET SOA protection REF LIMIT ISET SELECT Automatic retry or latch-off on current fault 1.0V CURRENT LIMIT Programmable current-limit timer for SOA CONTROL SS Programmable, multifunction GPO TIMER ON FLB Power-good status output TIMER TIMER TIMEOUT Analog UV and OV protection PWRGD LOGIC GPO2/ALERT2 SENSE+ ENABLE pin 12-BIT AND LATCH VOUT ADC IOUT PMBus SCL Reports power and energy consumption over time SDA ADR Peak detect registers for current and voltage GND PMBus fast mode compliant interface Figure 1. 20-lead LFCSP APPLICATIONS Power monitoring and control/power budgeting Central office equipment Telecommunication and data communication equipment PCs/servers FET and allows the safe operating area (SOA) to be adhered to GENERAL DESCRIPTION in an effective manner. The ADM1276 is a hot swap controller that allows a circuit board In case of a short-circuit event, a fast internal overcurrent to be removed from or inserted into a live backplane. It also features detector responds within 370 ns and signals the gate to shut current and voltage readback via an integrated 12-bit analog-to- down. A 1500 mA pull-down device ensures a fast FET response. digital converter (ADC), accessed using a PMBus interface. The ADM1276 features overvoltage (OV) and undervoltage (UV) The load current is measured using an internal current sense protection, programmed using external resistor dividers on the amplifier that measures the voltage across a sense resistor in UV and OV pins. A PWRGD signal can be used to detect when the power path via the SENSE+ and SENSE pins. A default the output supply is valid, using the FLB pin to monitor the output. limit of 20 mV is set, but this limit can be adjusted, if required, A GPO pin can be configured as an output signal that can be using a resistor divider network from the internal reference asserted when a programmed current or voltage level is reached. voltage to the ISET pin. The 12-bit ADC can measure the current in the sense resistor, The ADM1276 limits the current through the sense resistor by as well as the supply voltage on the SENSE+ pin or the output controlling the gate voltage of an external N-channel FET in the voltage. A PMBus interface allows a controller to read current power path, via the GATE pin. The sense voltageand, therefore, and voltage data from the ADC. Measurements can be initiated the load currentis maintained below the preset maximum. The by a PMBus command. Alternatively, the ADC can run conti- ADM1276 protects the external FET by limiting the time that the nuously, and the user can read the latest conversion data whenever FET remains on while the current is at its maximum value. This required. As many as four unique PMBus addresses can be selected, current-limit time is set by the choice of capacitor connected to depending on the way that the ADR pin is connected. the TIMER pin. In addition, a foldback resistor network can be LATCH The ADM1276 is available in a 20-lead LFCSP with a pin used to actively lower the current limit as the voltage across the that can be configured for automatic retry or latch-off when an FET is increased. This helps to maintain constant power in the overcurrent fault occurs. Rev. C Document Feedback 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 One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. rights of third parties that may result from its use. Specifications subject to change without notice. No Tel: 781.329.4700 20112013 Analog Devices, Inc. All rights reserved. license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Technical Support www.analog.com Trademarks and registered trademarks are the property of their respective owners. 09718-001ADM1276 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Power Monitor Commands ...................................................... 28 Applications ....................................................................................... 1 Warning Limit Setup Commands ............................................ 29 General Description ......................................................................... 1 PMBus Direct Format Conversion .......................................... 30 Functional Block Diagram .............................................................. 1 Voltage and Current Conversion Using LSB Values .............. 32 Revision History ............................................................................... 3 ALERT2 GPO2/ Pin Behavior ....................................................... 33 Specifications ..................................................................................... 4 Faults and Warnings .................................................................. 33 Serial Bus Timing Characteristics .............................................. 7 Generating an Alert ................................................................... 33 Absolute Maximum Ratings ............................................................ 8 Handling/Clearing an Alert ...................................................... 33 Thermal Characteristics .............................................................. 8 SMBus Alert Response Address ............................................... 33 ESD Caution .................................................................................. 8 Example Use of SMBus Alert Response Address ................... 34 Pin Configuration and Function Descriptions ............................. 9 PMBus Command Reference ........................................................ 35 Typical Performance Characteristics ........................................... 11 OPERATION .............................................................................. 36 Typical Application Circuit ........................................................... 17 CLEAR FAULTS ........................................................................ 36 Theory of Operation ...................................................................... 18 CAPABILITY .............................................................................. 36 Powering the ADM1276 ............................................................ 18 VOUT OV WARN LIMIT ..................................................... 36 Current Sense Inputs .................................................................. 18 VOUT UV WARN LIMIT ..................................................... 36 Current-Limit Reference ........................................................... 19 IOUT OC WARN LIMIT ...................................................... 36 Setting the Current Limit (ISET) ............................................. 19 IOUT WARN2 LIMIT ............................................................. 36 Soft Start ...................................................................................... 20 VIN OV WARN LIMIT ......................................................... 37 Foldback ....................................................................................... 20 VIN UV WARN LIMIT ......................................................... 37 Timer ............................................................................................ 21 PIN OP WARN LIMIT .......................................................... 37 Hot Swap Retry Duty Cycle ...................................................... 21 STATUS BYTE .......................................................................... 37 FET Gate Drive Clamps ............................................................. 21 STATUS WORD ........................................................................ 38 Fast Response to Severe Overcurrent ...................................... 22 STATUS VOUT ......................................................................... 38 Undervoltage and Overvoltage ................................................. 22 STATUS IOUT .......................................................................... 38 ENABLE Input ............................................................................ 22 STATUS INPUT ........................................................................ 39 Power Good ................................................................................. 22 STATUS MFR SPECIFIC ........................................................ 39 VOUT Measurement ................................................................. 23 READ EIN .................................................................................. 40 FET Health .................................................................................. 23 READ VIN ................................................................................. 40 Power Monitor ............................................................................ 23 READ VOUT ............................................................................. 40 PMBus Interface ............................................................................. 24 READ IOUT .............................................................................. 40 Device Addressing ...................................................................... 24 READ PIN .................................................................................. 40 SMBus Protocol Usage ............................................................... 24 PMBUS REVISION .................................................................. 40 Packet Error Checking ............................................................... 24 MFR ID ....................................................................................... 41 SMBus Message Formats ........................................................... 25 MFR MODEL ............................................................................ 41 Group Commands ...................................................................... 26 MFR REVISION ........................................................................ 41 Hot Swap Control Commands ................................................. 27 PEAK IOUT ............................................................................... 41 ADM1276 Information Commands ........................................ 27 PEAK VIN.................................................................................. 41 Status Commands ....................................................................... 27 PEAK VOUT ............................................................................. 42 GPO and Alert Pin Setup Commands ..................................... 28 PMON CONTROL ................................................................... 42 Rev. C Page 2 of 48