Aspects of the disclosure provide for a circuit. In some examples, the circuit includes a first current source having a terminal coupled to a first node and a second terminal, a first switch coupled between the second terminal of the first current source and a second node, a first resistor coupled between the second node and a ground terminal, a second current source having a terminal coupled to the first node and a second terminal, a second switch coupled between the second terminal of the second current source and a third node, a second resistor coupled between the third node and the ground terminal, a third current source having a terminal coupled to the first node and a second terminal, a third switch coupled between the second terminal of the third current source and a fourth node, and a third resistor coupled between the fourth node and the ground terminal.