Activeload Design Solution And Its Application Under IC Autotest System

This document illustrates the theory of operation for the configurable powersupply module used on test automation system. This module contains sixchannels of power supplies， whose parameters including output voltage，power-on sequence and ramp-up time can be configured separately. Inaddition， the status of each channel can be monitored. The module can beplugged into a slot and it communicates with the central controller throughbackplane connector. A pre-defined SPI-like communication protocol isapplied to guarantee the successful command and data exchange.The output voltage of each power rail is adjustable through a digitalpotentiometer， which has a digital interface with the MCU. The variablesoft-start capacitorCSScontrols the ramp-up time of the switch regulator， andits capacitance is controlled by the MCU also. MCU is the most importantpart of the whole system. Features&Specifications: Number of Power Rails:6; Output Voltage Range:0.8V~4.0V; Maximum output current per powerrail:3A; Voltage and Current Monitoring; Ramp-up Time Configurable; Power-on Sequence Configurable; Two On-board Clocks with FixedFrequency (Single-end and differential respectively); One On-board Clockwith Configurable Frequency; One Input Channel for Measuring ExternalClock; Hot-swap of the board.Either MCU/DSP or FPGA can be used as micro-processor on board.The main functionalities of the micro-processor are: Communicate with thecontroller through backplane connector. Each module has a standardbackplane connector and all the communicate signals transmit through thatcomplying with a pre-defined SPI-like protocol. Write the digitalpotentiometer to set the output voltage according to the voltage configuration;sample the voltage and adjust the digital potentiometer over and over. Samplethe load current for each power rail and store the result for software inquiry.Set the ramp-up rate for each power rail by adjusting the variable capacitors.Implement the power-on sequence for all the power rails. Set the DDSparameters and adjust the output clock frequency.