System for diagnosing impedances having accurate current source and accurate voltage level-shift

摘要

The present invention relates to a system for measuring a capacitor (C). A current source (12) is connected in parallel to the capacitor (C) between a supply plane (Vc) and ground (VGND) for providing a current to the capacitor (C). A voltage level-shift is connected between the supply plane (Vc) and the ground (VGND) in parallel to the capacitor (C) and in parallel to the current source (I2). The voltage level-shift senses a voltage across the electronic component (C) and provides a level-shifted output voltage Vout in dependence thereupon. The voltage level-shift comprises a resistor (RI) connected in series with a current source (II) and an output port interposed between the resistor (RI) and the current source (II). The current sources (I,) and (12) have opposite temperature coefficients such that the current provided to the electronic component is substantially constant.