Hot Swap Controller and Digital Power and Energy Monitor with PMBus Interface
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, and power 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, using a resistor divider network from the internal reference voltage to the ISET pin.
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 the safe operating area (SOA) limits. A programmable start-up current limit is also available for dv/dt power-up.
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 12-bit ADC can measure the current in the sense resistor, the supply voltage on the HS+ pin, the output voltage, and the temperature at the external NPN device. A PMBus interface allows a controller to read data from the ADC. As many as 16 unique I2C addresses can be selected, depending on how the two ADRx pins are connected.
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.
- Power monitoring and control/power budgeting
- Central office equipment
- Telecommunication and data communication equipment
This product has been released to the market. The data sheet contains all final specifications and operating conditions. For new designs, ADI recommends utilization of these products.
Four sense-resistor slots and six multipackage FET slots give users great flexibility and allow a wide range of application setups.
Multiple test points allow easy access to all critical points/pins. Seven LEDs give users direct visual indication on variations in the board status, such as supply input, output, IC power good output, fault output, current sense output, and GPO outputs. An AD7291 8-channel, I2C, 12-bit SAR ADC allows users to measure voltage such as CSOUT and other pin voltages as well as to read ambient board temperature through an I2C bus in real time.
The kit supports I2C communication, allowing users to communicate with the ADM1278. The evaluation kit also supports cascade setup so multiple evaluation boards can be connected together and share the same I2C bus.
The standard evaluation kit is prepopulated and tested with a 12 V, 73A hot swap design capable of working with a 3 mF output capacitor.
Complete specifications for the ADM1278 are available in the ADM1278 data sheet from Analog Devices and should be consulted in conjunction with this user guide when using the evaluation boards.
- EVAL-ADM1278EBZ evaluation board
Additional Hardware Needed
- Serial I/O interface USB-SDP-CABLEZ (not included in the evaluation kit and should be ordered separately)
- Only one dongle is required in multiboard cascade setup
- Analog Devices, Inc., hot swap and power monitoring evaluation software
Hot-Swap & Power Monitoring Evaluation Software
ADMxxxx Common Run-Time