Floating Constant Current Constant Voltage Source For Testing Of Analog Integrated Circuits

Analog IC test is based on the standard-driven,so DC voltage and current test is being widely used in analog IC testing. The two most common methods of analog IC testing are FVMI(force voltage and measure current) and FIMV(force current and measure voltage)。Therefore, the equipment which could force constant current and voltage to DUT (device under test) and could measure the voltage and current of DUT is critical for analog IC test technology. This article is dedicated to inventing such voltage and current source. In the article, constant current and voltage circuit consists of operational amplifier (OPA), the power OPA provide high voltage and current that DUT required, force current and voltage are measured by instrument OPA and feeded back to the input port in order to stabilize the output. The output value (current or voltage) is determined by the computer and converted to analog signal by high-precision D/A converter. DUT's current and voltage is sampled by high-precision A/D converter. In this article a FPGA (field programble gate array) is used to accomplish the control function.This voltage and current source can provide daul independent channel, each channel is capable of forcing and measuring up to±16v and±400mA with 4 programmable voltage range and 7 programmable current range. The accuracy of voltage forcing and measuring is 0.1% and the accuracy of current is 0.2%. Comparator outputs are provided per channel for device go no-go testing and used in the situation that the users merely care about test speed but not the specific test data. Meanwhile, the clamp circuit will limit the output voltage or current at a fixed value when they are abnormal that caused by a DUT short circuit or other fault in order to protect the device. In additional, one of the most significant features of the module is floating sense.This module is controlled by a system ground referenced digital interface, but the main output circuit is fioating ground. This function is carried out through the DC / DC converter combined with the optocoupler.This paper is organized as follows: The first chapter is an introduction; it introduces the background and source of the project. The second chapter describes the blueprint of design and analysis the feasibility of the blueprint. The third chapter researches the float measuring technology and give out detailed circuit. The fourth chapter introduces the various parts of hardware design as well as the FPGA control logic circuit, analysises the stability of the feedback circuit and designs a phase compensation circuit for it. The fifth chapter describes the drivers and debugging software design.The sixth chapter gives out debugging data, analysises data error and adjusts the software using the least square method. In the last of the paper we give out the conclusions and outlook for further study.