Patent ID: 7630159
Filing Date: 2009-12-08
Classification: G11B

Abstract:
1. An apparatus for determining a sensor resistance wherein a voltage is applied across the sensor, comprising: a circuit producing a zero temperature coefficient current in response to a current drawn by the sensor or in response to a current related to the current drawn by the sensor; a first reference resistor receiving the zero temperature coefficient current, a voltage developing across the first reference resistor in response to the zero temperature coefficient current wherein the voltage developed across the first reference resistor comprises an absolute voltage; and a comparator having a first terminal responsive to a predetermined voltage and a second terminal responsive to the voltage developed across the first reference resistor, the comparator producing a signal indicative of the sensor resistance when a difference between the predetermined voltage and the voltage developed across the first reference resistor exceeds a detection threshold of the comparator, wherein the detection threshold of the comparator is determined by the first reference resistor, the zero temperature coefficient current and an absolute current, such that the detection threshold of the comparator is substantially independent of process and temperature variations.