Patent ID: 8283876

Claim:
A method for driving an infrared transmitter LED with temperature compensation for a circuit comprising the following steps: (1) providing one or more LED diodes, a battery voltage, an analog-to-digital converter, a LED driver comprising a resistive digital-to-analog converter structure controlling a current through the diodes, wherein the digital-to-analog converter structure comprises a coarse DAC inputting all bits of the output of the coarse DAC to a fine DAC, a circuit to measure a battery voltage and a difference of forward diode voltages, a programmable current sink, a circuit for offset cancellation, and a circuit for resistor load compensation; (2) calibrating the analog-to-digital converter by canceling an offset between a battery voltage and a forward voltage of said one or more LEDs; (3) determining if the battery voltage is in an acceptable range; (4) determining temperature dependency of the forward voltage of said one or more LEDs by comparing the forward voltages when switching a drive current between two constant current values; and (5) adjusting a driver current of said one or more LEDs according to the temperature dependency wherein the driver current is adjusted using the resistive digital-to-analog converter structure.