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04-19-2017 09:55 AM
I was wondering what does the DCDCBIASEN bit in the LCD0_Config Register do? I can see reference in the SIM3l1XX Reference manual that it needs to be turned on when starting up the DCDC module but does it have to stay on after the DCDC module is up and running.
0: Disable the secondary bias current output
1: Enable the secondary bias current output.
We had some test firmware that was clearing the bit when the display was powered off and not enabling it when the display was turned back on. The side effect was that when we entered PM8 with the bit cleared the micro draws less current. I cannot find anything that describes what disabling the secondary bias current output has on the rest of the system. Is it ok to disable it once the DCDC converter is up and running? Is it ok to turn it off before going into PM8 and re enabling it once we leave PM8. During out testing the BIASEN line is set to enable.
We are keeping the display on during this operation and visually I do not see any adverse effects on the system by disabling the secondary bias current output.
04-20-2017 10:14 AM - edited 04-20-2017 10:35 AM
You're right - I don't see anything in our documentation for this bit outside of the DCDC startup procedure. I'll need to talk with our design team to see if this bit can be cleared after the DCDC starts up.
Edit: I've put in an internal ticket to request this information from the design team: MCUDSR-169. I'll let you know when I receive a response from them.