Patent ID: 6845048

Claim:
A system for monitoring voltage levels of a plurality of internal voltage sources on an integrated circuit comprising: an analog multiplexing circuit integrally formed on the integrated circuit having a plurality of inputs and an output, wherein each input of the plurality of inputs of the analog multiplexing circuit is in communication with a respective voltage source of the plurality of internal voltage sources through a respective input resistor of a plurality of input resistors, and wherein the analog multiplexing circuit has a plurality of control lines for enabling a respective input of the plurality of inputs of the analog multiplexing circuit; an analog-to-digital converter integrally formed on the integrated circuit having an input and at least one output, wherein the input of the analog-to-digital converter is in communication with the output of the analog multiplexing circuit; and an interface circuit integrally formed on the integrated circuit having at least one input and at least one output, wherein the at least one input of the interface circuit is in communication with the at least one output of the analog-to-digital converter, and wherein the at least one output of the interface circuit provides a digital representation of the voltage levels; and wherein the analog multiplexing circuit has a plurality of voltage followers, wherein each voltage follower of the plurality of voltage followers has an output and an input, and wherein each input of the plurality of inputs of the analog multiplexing circuit comprises the input of a respective voltage follower, and wherein each input of the plurality of inputs of the analog multiplexing circuit further comprises a transistor having a gate, wherein the transistor communicates a voltage at the input of the analog multiplexing circuit to the input of the respective voltage follower in response to a signal on the gate, and wherein the gate is in communication with a respective control line of the plurality of control lines, such that when the transistor is conducting, the corresponding input resistor is a load for the corresponding voltage source, the conducting transistor provides a path between the input of the voltage follower and ground, and the potential at the output of the voltage follower is approximately zero.