In this article we detail the process of measuring a key performance characteristic of voltage references, power supply rejection ratio or “PSRR”, using the Picotest J2120A Line Injector and the OMICRON Lab Bode 100 VNA.
There are many types of voltage references, including series references, shunt references and several that can perform as either series or parallel devices. The general performance metrics include DC voltage accuracy, temperature coefficient, noise, output impedance, PSRR and stability. The requirements vary greatly from application to application, though the general characteristics remain the same.
PSRR is a significant performance concern as even small amounts of high frequency ripple voltage at the input can significantly degrade the output precision of the device and impact downstream circuitry. The stability of the reference plays a large role in the PSRR and for that reason the measurements in this application note are performed with and without a small ceramic output capacitor across the reference output.