Method of testing a power supply controller and structure therefor

1. A method of testing a power supply controller comprising:

coupling an output signal from an output of an error amplifier of the power supply controller to an impedance translator including coupling the output signal from the output of the error amplifier to a feedback circuit of the power supply controller; and

measuring a value of an output signal of the impedance translator.

2. The method of claim 1 wherein coupling the output signal from the output of the error amplifier includes stopping a clock of the power supply controller from generating a clock signal.

3. The method of claim 1 wherein coupling the output signal from the output of the error amplifier includes de-coupling the output signal of the impedance translator from a PWM controller of the power supply controller.

4. The method of claim 1 further including adjusting a value of the output signal of the impedance translator to compensate for offset errors of the error amplifier, and again coupling the output signal from the output of the error amplifier of the power supply controller to the impedance translator, and measuring the value of the output signal of the impedance translator.

5. A method of testing a power supply controller comprising:

coupling an output signal from an output of an error amplifier of the power supply controller to an impedance translator including translating the output signal from a high output impedance of the error amplifier to a low output impedance of the impedance translator; and

measuring a value of an output signal of the impedance translator.

6. The method of claim 5 wherein coupling the output signal from the output of the error amplifier includes inhibiting the power supply controller from coupling a PWM drive signal to a power switch of the power supply controller.

7. The method of claim 6 wherein inhibiting the power supply controller from coupling the PWM drive signal to the power switch includes inhibiting the power supply controller from generating PWM drive signals.

8. A power supply controller comprising:

an error amplifier having a first input, a second input, and an output; and

a test mode controller configured to couple the first input of the error amplifier to receive a signal representative of an output signal of the error amplifier, the test mode controller including an impedance translator wherein the test mode controller is configured to couple the output signal of the error amplifier to an input of the impedance translator and to couple an output signal of the impedance translator to the first input of the error amplifier in a test mode and to not couple the output signal of the error amplifier through the impedance translator to the first input of the error amplifier in the normal mode.

9. The power supply controller of claim 8 further including the test mode controller configured to couple a signal representative of the output signal of the error amplifier to a terminal of the power supply controller.

10. The power supply controller of claim 8 further including the test mode controller configured to inhibit the power supply controller from generating PWM drive signals.