We recently had the opportunity to catch up with one of the movers and shakers in the world of compliance testing: Andy Baldman. In addition to his role at UNH-IOL where he oversees one of the industry’s leading compliance labs for MIPI® devices, Andy also serves as chair of the MIPI Conference Test Subgroup and is the Vice-Chair of the PHY Subgroup. What’s more, he is the author of the D-PHY, C-PHY and M-PHY physical layer conformance test specifications.
Based on these qualifications, it’s safe to say that Andy has good insight into major developments that involve MIPI device testing. One of the areas receiving a lot of attention, according to Andy, is the new C-PHY spec published last year. With its unique 3-pin, 3-lane architecture it’s easy to see why. In a short Q&A Andy touches on C-PHY challenges, the evolution of MIPI test specifications, and the role of arbitrary waveform generators (AWGs) in compliance testing. Here’s the interview.
What are some of the biggest challenges you see for the MIPI device testing and why?
The new signaling types such as C-PHY pose the biggest challenges, in terms of signal generation for RX testing. Traditional BERTs cannot easily be used to generate the 3-line, 3-level signaling required by C-PHY, without a large number of combined channels and external hardware.
How are compliance test specifications (CTS) evolving to simplify PHY tests and yet make sure there is a good coverage of tests?
As each CTS evolves, we are trying to eliminate lower-value test cases, and combine test cases where possible, to simplify complexity and decrease test time, without sacrificing major test coverage. For example, for C-PHY, we eliminated the common-mode interference tests, as these would be additionally challenging to calibrate accurately for a 3-wire system. Also, we have adopted an eye-diagram-based calibration procedure for C-PHY RX jitter tolerance testing, and combined it with the static common-mode tolerance measurement, which should further reduce overall complexity.
In your opinion how suitable is an AWG for MIPI RX testing? What are your thoughts around testing RX using AWGs?
The newest generation of AWG's on the market, when combined with good configuration software, offer speed and flexibility that is very well-suited for performing C/D/M-PHY RX testing, greatly reducing complexity and test time.
Any highlights about what happening around MIPI at UNH-IOL?
The existence of capable signal generation solutions for C-PHY are a driving force in allowing us to offer new conformance and characterization test services for C-PHY, in addition to our existing D-PHY and M-PHY test services.