In an embodiment a semiconductor device includes a first diode and a second diode of specified sizing or biasing ratio, a negative voltage supply, a first resistor for a proportional to absolute temperature (PTAT) voltage drop, wherein the first diode is connected between the negative supply voltage and the first resistor, an array of dynamically matched current sources employing a dynamic element matching controller, wherein the first resistor is connected between the first diode and a first input of the array, and wherein the second diode is connected between the negative supply voltage and a second input of the array and a successive approximation register (SAR) feedback loop configured to drive a voltage difference to zero, wherein the voltage difference occurs between a first node present between the first resistor and the first input of the array and a second node present between the second diode and the second input of the array.