We took delivery yesterday of a large shipment of assembled PCBs including 500 ProgRock2 modules and the overheating problem of the previous batch is now SOLVED.?
ProgRock2 was plagued by a significant percentage which did not work, the Microchip MIC5219 voltage regulator chip failed, not delivering the correct 3.3V output voltage and just getting very hot and burning up. Big thanks are due to Clark?W7WRX who did some detective work and also contacted engineers at Microchip, uncovering a design flaw. There is supposed to be a capacitor at the input to the voltage regulator and without it, under some circumstances instability can occur. The capacitor keeps everything stable, but I forgot it :-/? ?
The first batch of ProgRock2 were mysteriously OK. The second batch, a significant proportion - maybe 20-30% - suffered this failure here during testing. Evidently some device-to-device variations make it more or less likely. So of course we put those to one side and never shipped them; but nevertheless still a number of customers complained of burned up regulator chips in the field.?
Suffice it to say that ProgRock2 Rev 2 now has a 10uF MLCC at its input.?
Yesterday we programmed one ProgRock2 and I tested it successfully, which was encouraging but a sample size of one, not statistically significant. This morning my colleague has programmed and tested 59 of the batch of 500 (so far), and 59 successfully. So we can confidently say the problem is solved now.?
