Method of forming D/A resistor strings with cross coupling switches

摘要

A method is disclosed for forming resistor strings in a semiconductor material for a digital-to-analog converter having a main DAC resistor string and a sub-DAC resistor string. The main DAC resistor string is formed as two identical resistor strings connected in parallel and such that the bottom of one resistor string and the top of the other resistor string are connected to a first voltage. The other ends of the resistor strings are coupled to a second different voltage. A switch multiplexer serving two functions is connected between the resistor strings. Each switch of the multiplexer interconnects similar voltage nodes of each resistor string together to thereby average the voltage should the resistance values differ due to semiconductor process variations. The switch multiplexer also serves to select one resistor of each resistor string to couple the voltage thereacross to a sub-resistor string of the digital-to-analog converter.