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ADM1278-1AACPZ Datasheet(PDF) 1 Page - Analog Devices |
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ADM1278-1AACPZ Datasheet(HTML) 1 Page - Analog Devices |
1 / 61 page Hot Swap Controller and Digital Power and Energy Monitor with PMBus Interface Data Sheet ADM1278 FEATURES ±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 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 APPLICATIONS Servers Power monitoring and control/power budgeting Telecommunication and data communication equipment TYPICAL APPLICATION CIRCUIT GATE Q1 MO+ HS+ HS– TIMER TIMER ADM1278-1 MO– RSENSE 4.5V TO 20V VCC VCP VCAP ISENSE UV OV 1.0V 1.0V TEMP VOUT PWGIN 1.0V VOUT 12-BIT ADC SCL SDA ADR2 ISENSE HS+ TEMP LDO CHARGE PUMP TIMEOUT IOUT GPO1/ALERT1/CONV ENABLE GPO2/ALERT2 VCBOS ISTART ISET PSET TIMEOUT CURRENT- LIMIT CONTROL REF SELECT 1.0V HS– FAULT RETRY PWRGD ADR1 CSOUT GATE DRIVE/ LOGIC LOGIC AND PMBus ANALOG VOUT ×50 + + + + – – – – + – GND PGND 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. 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. 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 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. Table 1. Model Options Model ADC Accuracy SPI Interface Enable Pin1 ADM1278-1AA ±0.3% No Active high ADM1278-1A ±0.7% No Active high ADM1278-1B ±1.0% No Active high ADM1278-2A ±0.7% Yes Active high ADM1278-3A ±0.7% No Active low 1 Active high relates to the ENABLE pin, and active low relates to the ENABLE pin. Rev. A Document Feedback Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibilityisassumedbyAnalogDevicesforitsuse,norforanyinfringementsofpatentsorother rightsofthirdpartiesthatmayresultfromitsuse.Specificationssubjecttochangewithoutnotice.No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarksandregisteredtrademarksarethepropertyoftheirrespectiveowners. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 ©2014 Analog Devices, Inc. All rights reserved. Technical Support www.analog.com |
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