Patent ID: 6977510
Filing Date: 2005-12-20
Classification: G01R

Abstract:
1. A circuit to measure very precisely the resistance of a small resistor independent from process and temperature variations is comprising: a constant current source; a resistor to be measured, wherein a first terminal of the resistor is connected to said current source, to a first input of a third means to clamp voltage and via a switch to any application circuitry, and a second terminal is connected to a first means to clamp voltage and via another switch to an application circuitry, wherein said both switches are open during a resistance measurement of the resistor; a pair of switching means, wherein each of the switching means is between one terminal of said resistor to be measured and a circuitry of any application; a first means to clamp voltage having two inputs and an output, wherein the first input is a reference voltage and the second input is a feedback from the output of said means to clamp voltage and wherein the current provided by said current source is flowing through the first means to clamp a voltage to ground and its output is connected to a first input of a second means to clamp a voltage; a second means to a clamp a voltage having two inputs and an output, wherein the first input is the output of said first means to clamp a voltage and the second input is a feedback from its own output and it is generating at its output a current I a first, a second and a third resistor all are having the same resistance; a first current mirror comprising a first and a second PMOS transistor, having both the same size, mirroring said current I a third means to clamp a voltage having two inputs and an output, wherein the first input connected to a first terminal of said resistor to be measured and the second input is a feedback from its own output and it is generating at its output a current I a current mirror comprising a first and a second PMOS transistor, having a gain n, mirroring said current I an analog-to digital converter converting said output voltage to digital values.