Abstract: In an embodiment, a semiconductor device is disclosed. The semiconductor device includes a plurality of output pins. Each of the output pins is electrically connected to an input pin of a buzzer and to a buzzer driver. The buzzer driver is configured to cause the buzzer to emit an audible sound. The semiconductor device further includes a plurality of ground switches. Each ground switch is configured to connect a corresponding output pin of the plurality of output pins to ground when closed. The semiconductor device further includes a current generator that is configured to supply a test current to a given output pin of the plurality of output pins and a clamp switch that is configured to connect the given output pin to an analog-to-digital converter.

Abstract: An integrated circuit includes a self-calibrating resistor circuit comprising a resistor string, a comparator, a state machine, a reference voltage source, and a reference current source. The current source typically comprises a voltage reference, typically a bandgap reference, and a temperature-independent resistor having a value REXT. In operation, a reference current IREF flows through the resistor string. During a calibration period, the voltage across the string is compared to the bandgap reference voltage, VBG, by the comparator, which controls the state of the state machine. The outputs of the state machine turn on or off the resistors in the string until the voltage across the string, VR, is approximately equal to the reference voltage. The resistance of the resistor string is then equal to RBG=VBG/IREF, which is proportional to REXT, and thus is typically independent of process and temperature.