Patent ID: 7773715

Claim:
A transmitter that controls a loop current, comprising: positive and negative leads carrying the loop current, the loop current including first, second, third and fourth currents in the transmitter; a loop current controller that includes a resistor that carries the first current and that controls the first current as a function of both a process variable and a sense voltage at the resistor; a first regulator coupling to the positive lead, providing a first voltage, and coupling the second current through the resistor; a second regulator coupling to the first voltage, providing a second voltage, and coupling the third current through the resistor; a first load that carries a first load current between the first voltage and the second voltage; a second load that includes a controller area network load, and that couples a second load current between the second voltage and the negative lead, the second load current bypassing the resistor; and the loop current controller sensing the second voltage to correct the first current for the load current that bypasses the resistor.