How to Test PSRR, PSNR and PSMR for Sensitive Applications, Including Optical Transceivers

The impact of power supply noise on high performance systems is well established, and as a result, many applications now require power supply sensitivity testing to assure robust designs.  There are numerous obstacles to overcome, beginning with nomenclature.  Different applications use different naming conventions for power supply sensitivity.  In power electronics, we refer to this as PSRR or Power Supply Ripple Rejection, while in RF we refer to this as PSMR or Power Supply Modulation Ratio, and in high-speed transceivers we refer to this as PSNR or Power Supply Noise Rejection.

The most recent QSFP-DD optical transceiver specification, for example, requires noise to be injected onto the power supply input over a frequency range of 40Hz-10MHz.  This is challenging at the very least, leaving engineers to not only perform the test, but to develop the methods and equipment required.

In this session, I will present the requirements, measurement challenges, and proposed solution, including the test setup, for performing these difficult tests.