In an example, a device comprises a first resistor coupled to a second resistor and to a trim resistor, the second resistor and the trim resistor coupled to a port configured to couple to a third resistor. The device also comprises a comparator having an inverting input coupled to a first node between the second resistor and the port and a non-inverting input coupled to a second node between the first resistor and the trim resistor. The device further includes a trim control circuit coupled to an output of the comparator and having an output coupled to the trim resistor, the trim control circuit configured to couple to multiple integrated trim resistors external to the device.