ADI公司的ADM1278是具有PMBus接口的热插拔控制器和数字电源与能量监视器, 允许电路板插入或拔出带电的背板, 集成的12位ADC用来检测IOUT,VIN,VOUT和温度,精度±0.3%,短路的响应时间320ns,主要用在服务器,电源功率监视和控制/功率预算,通信和数据通信设备以及中心局设备.本文介绍了ADM1278主要特性,功能框图和典型应用电路,以及ADM1278评估板EVAL- ADM1278EBZ主要特性,基本框图,电路图,材料清单和PCB元件布局图.
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.
±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
Split hot swap and power monitor inputs to allow additional external ADC filtering
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 and OV thresholds
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
Power monitoring and control/power budgeting
Central office equipment
Telecommunication and data communication equipment
The EVAL-ADM1278EBZ is a compact full feature evaluation board for the ADM1278. The board layout gives users a clear visual of all the peripheral components and the hot swap power path. The layout also maximizes the board’s ability to dissipate heat for some of the key components on the power path, allowing the evaluation of very high current hot swap setups.
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 boards are fully compatible with the ADM1278 evaluation software tool, which can be downloaded from the ADM1278 product page.
Users need a USB-SDP-CABLEZ USB-to-I2C dongle to use the evaluation software tools.
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.
Fully functional support evaluation kit for the ADM1278
Populated and tested with 12 V, 73 A, 3 mF design
Special N-MOSFET footprint suits different packages
Supports up to four 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