Linear, low-latency power supply monitor

A power supply monitor comprising:

• a resistor having a first terminal for receiving a power supply voltage to be measured, and a second terminal;
• a first current mirror having an input coupled to said second terminal of said resistor, and an output;
• a second current mirror having an input coupled to said output of said first current mirror, and an output;
• and
• a current-controlled oscillator having an input coupled to said output of said second current mirror, and an output for providing a frequency signal;
• a time-to-digital converter having an input coupled to said output of said current-controlled oscillator, and an output for providing a count signal representative of a number of cycles of a reference clock signal per cycle of said frequency signal, wherein said time-to-digital converter inserts a non-linearity into an overall transfer function of the power supply monitor;
• and
• an output divider having an input coupled to said output of said time-to-digital converter, and an output for providing a divided count signal representative of a value of said power supply voltage, wherein said output divider provides said divided count signal by dividing a fixed number by said count signal, wherein said output divider corrects said non-linearity caused by said time-to-digital converter such that said overall transfer function of the power supply monitor is highly linear.

A method comprising:

• receiving a power supply voltage to be measured;
• generating a frequency signal having a frequency linearly proportional to said power supply voltage;
• providing a count signal representative of a number of cycles of a reference clock signal per cycle of said frequency signal, wherein said providing comprises using a time-to-digital converter that inserts a non-linearity into an overall transfer function;
• and
• dividing a fixed number by said count signal to provide a divided count signal representative of a value of said power supply voltage, wherein said dividing corrects said non-linearity caused by said providing said count signal using said time-to-digital converter such that said overall transfer function is highly linear.