Power supply monitoring

A method for monitoring a power supply configured to provide a supply voltage and for monitoring a bandgap circuit configured to generate a substantially fixed reference voltage using the supply voltage, the method comprising:

• providing an output voltage equal to the smaller of the reference voltage multiplied by a gain value and the supply voltage;
• responsive to the output voltage meeting a trigger value, providing first information indicating that the reference voltage meets a reference threshold value, and the supply voltage meets a supply threshold value;
• and
• responsive to the output voltage failing to meet the trigger value, providing second information indicating that the reference voltage fails to meet the reference threshold value or the supply voltage fails to meet the supply threshold value.

A supply monitoring circuit, comprising:

• an amplifier having a signal input configured to receive an reference voltage and a supply input configured to receive a power supply voltage;
• an open loop bandgap circuit comprising an input node coupled to an output of the amplifier, a first diode and a second diode;
• and
• a comparator having a first input coupled to the first diode and a second input coupled to the second diode.