Hot Swap Controller and Digital Power and Energy Monitor with PMBus Interface Data Sheet ADM1278 FEATURES TYPICAL APPLICATION CIRCUIT R Q 4.5V TO 20V SENSE 1 0.3% accurate, 12-bit ADC for I , V , V , and temperature OUT IN OUT 320 ns response time to short circuit HS+ MO+ MO HS Shutdown on detection of FET health fault VCC ADM1278-1 Constant power foldback for tighter FET SOA protection + 50 CHARGE VCAP Remote temperature sensing with programmable warning LDO PUMP I SENSE V UV CP and shutdown thresholds + GATE 1.0V GATE DRIVE/ Resistor-programmable 5 mV to 25 mV V current limit SENSE LOGIC OV TEMP Programmable start-up current limit TIMEOUT 1.0V + PWGIN 1% accurate UV, OV, and PWRGD thresholds ISET REF + SELECT PSET Split hot swap and power monitor inputs to allow additional 1.0V 1.0V CURRENT- LIMIT external ADC filtering ISTART HS CONTROL VOUT Reports power and energy consumption over time V CBOS Peak detect registers for current, voltage, and power PWRGD I OUT FAULT PROCHOT power throttling capability TIMER TIMER TIMEOUT ENABLE PMBus fast mode compliant interface LOGIC GPO2/ALERT2 HS+ AND GPO1/ALERT1/CONV I SENSE 12-BIT PMBus 5 mm 5 mm, 32-lead LFCSP SCL V ADC OUT SDA TEMP ADR1 RETRY APPLICATIONS ADR2 ANALOG CSOUT Servers VOUT Power monitoring and control/power budgeting PGND GND Telecommunication and data communication equipment Figure 1. GENERAL DESCRIPTION The ADM1278 is a hot swap controller that allows a circuit In case of a short-circuit event, a fast internal overcurrent board to be removed from or inserted into a live backplane. It also detector responds within 320 ns and signals the gate to shut features current, voltage, power, and temperature readback via an down. A 1500 mA pull-down device ensures a fast FET response. integrated 12-bit analog-to-digital converter (ADC), accessed The ADM1278 features overvoltage (OV) and undervoltage (UV) using a PMBus interface. The load current is measured using an protection, programmed using external resistor dividers on the internal current sense amplifier that measures the voltage across UV and OV pins. A PWRGD signal can be used to detect when the a sense resistor in the power path via the HS+ and HS pins. A output supply is valid, using the PWGIN pin to accurately default current limit of 20 mV is set, but this limit can be monitor the output. adjusted, if required. RETRY The ADM1278 is available in a 32-lead LFCSP with a pin The ADM1278 limits the current through the sense resistor by that can be configured for automatic retry or latch-off when an controlling the gate voltage of an external N-channel FET in the overcurrent fault occurs. power path, via the GATE pin. The sense voltage, and therefore the load current, is maintained below the preset maximum. The Table 1. Model Options 1 ADM1278 protects the external FET by limiting the time that Model ADC Accuracy SPI Interface Enable Pin the FET remains on while the current is at its maximum value. ADM1278-1AA 0.3% No Active high This current-limit time is set by the choice of capacitor connected ADM1278-1A 0.7% No Active high to the TIMER pin. In addition, a constant power foldback scheme ADM1278-1B 1.0% No Active high is used to control the power dissipation in the MOSFET during ADM1278-2A 0.7% Yes Active high power-up and fault conditions. The level of this power, along ADM1278-3A 0.7% No Active low with the TIMER regulation time, can be set to ensure that the 1 ENABLE Active high relates to the ENABLE pin, and active low relates to the pin. MOSFET remains within safe operating area (SOA) limits. 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. Tel: 781.329.4700 20142020 Analog Devices, Inc. All rights reserved. No license is granted by implication or otherwise under any patent or patent rights of Analog Technical Support www.analog.com Devices. Trademarks and registered trademarks are the property of their respective owners. 12198-001 + ADM1278 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 SMBus Protocol Usage .............................................................. 34 Applications ...................................................................................... 1 Packet Error Checking .............................................................. 34 2 Typical Application Circuit ............................................................ 1 Partial Transactions on I C Bus ............................................... 35 General Description ......................................................................... 1 SMBus Message Formats .......................................................... 35 Revision History ............................................................................... 3 Group Commands ..................................................................... 37 Specifications .................................................................................... 4 Hot Swap Control Commands ................................................. 37 Power Monitoring Accuracy Specifications ............................. 8 ADM1278 Information Commands ....................................... 37 Serial Bus Timing Characteristics .............................................. 8 Status Commands ...................................................................... 38 SPI Timing Characteristics (ADM1278-2) ............................... 9 GPO and Alert Pin Setup Commands .................................... 38 Absolute Maximum Ratings ......................................................... 10 Power Monitor Commands ...................................................... 39 Thermal Characteristics ............................................................ 10 Warning Limit Setup Commands ........................................... 40 ESD Caution................................................................................ 10 PMBus Direct Format Conversion .......................................... 40 Pin Configurations and Function Descriptions ......................... 11 Voltage and Current Conversion Using LSB Values ............ 41 Typical Performance Characteristics ........................................... 17 Alert Pin Behavior .......................................................................... 42 Theory of Operation ...................................................................... 24 Faults and Warnings .................................................................. 42 Powering the ADM1278 ............................................................ 24 Generating an Alert ................................................................... 42 Hot Swap Current Sense Inputs ............................................... 24 Handling/Clearing an Alert ...................................................... 42 Power Monitor Current Sense Inputs ..................................... 25 SMBus Alert Response Address ............................................... 43 Current-Limit Reference ........................................................... 25 Example Use of SMBus ARA.................................................... 43 Setting the Current Limit (ISET) ............................................. 26 Digital Comparator Mode ........................................................ 43 Setting a Linear Output Voltage Ramp at Power-Up ........... 26 Typical Application Circuits .................................................... 43 Start-Up Current Limit ............................................................. 27 PMBus Command Reference ....................................................... 45 Constant Power Foldback ......................................................... 28 Register Details ............................................................................... 46 Timer ............................................................................................ 28 Operation Register ..................................................................... 46 Hot Swap Retry ........................................................................... 29 Clear Faults Register .................................................................. 46 FET Gate Drive Clamps ............................................................ 29 PMBus Capability Register ....................................................... 46 Fast Response to Severe Overcurrent ...................................... 29 VOUT OV Warning Limit Register ............................................ 46 Undervoltage and Overvoltage ................................................. 29 V UV Warning Limit Register ............................................ 47 OUT Power Good ................................................................................ 29 I OC Warning Limit Register .............................................. 47 OUT FAULT OT Fault Limit Register............................................................. 47 Pin .................................................................................. 29 OT Warning Limit Register ...................................................... 47 ENABLE/ENABLE Input .......................................................... 30 VIN OV Warning Limit Register .............................................. 47 Current Sense Output (CSOUT) ............................................. 30 VIN UV Warning Limit Register .............................................. 48 Remote Temperature Sensing .................................................. 30 PIN OP Warning Limit Register ................................................ 48 SPI Interface ................................................................................ 31 Status Byte Register .................................................................... 48 VOUT Measurement ..................................................................... 32 Status Word Register ................................................................. 49 FET Health .................................................................................. 32 V Status Register ................................................................... 50 OUT Power Throttling ........................................................................ 32 I Status Register ..................................................................... 50 OUT Power Monitor ........................................................................... 32 Input Status Register .................................................................. 50 PMBus Interface ............................................................................. 34 Temperature Status Register .................................................... 51 Device Addressing ...................................................................... 34 Rev. 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