Design Of A Programmable Voltage Reference Circuit

As a high stability voltage standard, voltage reference has been widely used in digital appliances, intelligent instruments and testing systems. It has advantages such as steady, accurate, simple and convenient. Except for traditional circuit requirements, programmable voltage reference requires that its voltage can be preset and regulated accurately through external digital signals.With the development of IC design and semiconductor process, modern CPU integrated with more functions has more and more complex internal structure and consumes more power, thus requires much more on the power management. In this paper, a programmable voltage reference is designed for the DC-DC power management IC based on Bicmos technology. The output voltage to the CPU is determined with VID code according the VRM9.0 standard, its voltage adjustment step is 25 mV, voltage range is from 1.10 to 1.85V, and Output voltage error is±1%.Modules of the programmable voltage reference circuit, including the band-gap voltage reference, current reference, folded cascode operational amplifier and switch resistor network, are both analyzed in detail. Simulations are made with the Spectre and Hspice, and the results prove the feasibility of the proposed method. Layouts of the IC are completed with 0.8um 5V Bicmos process design rules. DRC and LVS documents validate the accuracy of the layouts.