View source for MISC-TN-027 — Qualifying a product for industrial, harsh environments: resilience against power supply anomalies

== Power supply anomalies resilience test ==
To make this test possible, DAVE Embedded Systems designed an ad hoc smart bench power supply denoted as PPSU. PPSU is used to power the DUT, which is the electronic device under test. You can think of PPSU as a programmable power waveform generator that is also able to verify the health status of the DUT. PPSU can generate an arbitrary supply voltage that exhibits purposely anomalies such as glitches and non-monotonic ramps. A robust product is expected to be resilient against these stressing conditions. For instance, the following picture shows a typical supply voltage used in such tests. After a regular 300ms 0-to-24V power-up ramp, the DUT is subject to four glitches that differ in terms of duration and amplitude.
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[[File:PPSU3-example1.png|center|thumb|600x600px]]<br>
  
In this context, by resilience we mean that either one of the following conditions occur:  
* DUT is not affected at all and continues to operate regularly  
* If it is inevitable that a hardware reset is triggered, DUT performs a warm reboot cycle and eventually returns to regular operating.  
Of course, the expected behavior depends strongly on the nature and severity of injected anomalies. After an anomaly is injected, PPSU verifies whether the DUT is operating properly or not and logs the test result. PPSU can also be programmed to run the test cycle repeatedly for the desired number of iterations and optionally to stop if the test fails.  

Combining several test waveforms of different types and running these tests over the entire DUT's operating temperature range allow to achieve good confidence that the product's power supply unit (PSU) will not fail in the field because of "misbehaving" power supply. Furthermore, these tests are extremely useful to detect hardware design errors or more subtle situations like the one described in [https://www.st.com/resource/en/application_note/an5861-stpmic1-auto-turnon-stmicroelectronics.pdf this application note] by ST Microelectronics. Thank to the use of PPSU, during the qualification of the [[ETRA SBC/General Information/Block Diagram and Features|ETRA Single Board Computer]], we had been able to spot the issue illustrated in this application note before STM released it publicly.