| 摘要 |
A circuit and a related method to measure very precisely the resistance Rm of a small resistor independent from process and temperature variations. This resistor may be the R<SMALLCAPS>ON </SMALLCAPS>resistance of an external sensor or e.g. the resistance of a safety device as a squib. A constant current source provides a current I<SMALLCAPS>BIAS </SMALLCAPS>causing a voltage drop Vm at the resistor to be measured. Using a configuration of operational amplifiers and current mirrors, wherein one of the current mirrors has a gain of n, an output voltage V<SMALLCAPS>OUT </SMALLCAPS>is achieved, which is defined by V<SMALLCAPS>OUT</SMALLCAPS>=nxRmxI<SMALLCAPS>BIAS</SMALLCAPS>. The gain n of a current mirror allows a very precise measurement of the resistance Rm of the resistor to be measured. The output voltage is finally converted from analog to digital values.
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