Voltage reference source for an overvoltage-tolerant bus interface

摘要

The invention relates to a voltage reference source used to control an overvoltage tolerant input/output buffer for a mixed voltage bus system. The voltage source comprises a voltage tracking circuit having a first input receiving a variable voltage, and a second input receiving a reference voltage, the voltage tracking circuit being adapted to generate an output voltage in response to the difference between the variable voltage and the reference voltage, wherein where the variable voltage is less than the reference voltage, the output voltage is held at substantially zero volts. When the variable voltage exceeds the reference voltage, the output tracks the voltage at the variable voltage input.