On-Chip Supply Voltage Measurement Technique

Supply voltage scaling in sub-micron circuits reduces the available voltage swing in both analog and digital circuits. For analog circuits, in particular, the dynamic range is often designed to cater to the worst case minimum supply voltage. To maximize the dynamic range performance it is useful if the actual supply voltage can be measured and the internal voltage swings optimized accordingly. Supply voltage measurement techniques are presented and one based on re-use of standard supply supervisory circuit (POR, UVD etc) in conjunction with DSP controller is discussed. First order analysis applied to 1.8V nominal supply case shows that with simple resistor divider interpolation, it is possible to achieve measurement resolution of about 20mV (1.2%). The concept can be extended for more range or resolution