What is the purpose of EN_DCDC and FB_DCDC (respectively 1.2_Reg_EN and 1.2V_Reg_FB in the images below)? What controls the EN line? Does our software control it? Is 1.2V needed for programming? We ask because it doesn’t appear to be on during programming on any board. It seems to be on in normal operation on boards that program, but not during programming.
We have approx. 15% of boards not programming. 5V and 3.3V look clean.
We’ve tried touching up solder, and tried rigging the 1.2V regulator on by tying pin 4 of U302 to 3.3V, which forced it on, but it didn’t improve the programming situation.
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- image001.png (16.66 KiB) Viewed 73 times
(We are aware the TPS62A02 was not on the hardware design guidelines list of compatible regulators--this guidelines document came out after we had already spun our first board revision, the first two board revisions seemed to work well)
