Other Parts Discussed in Thread: TPS65987D, , BQSTUDIO, TPS65987
I'm having an issue in which the En_OtG (bit #4 of Reg. 0x35) clears upon the instant that I make the OtG/VAP pin (#5) high, and as long as such pin is high, I can't set such bit high again and thus can't activate OtG. Of course, I also have the OtG_VAP_Mode (bit #5 of Reg. 0x34) high and appropriately set the OtG Voltage Register to 5.009V and the OtG Current register to 500mA. I normally use the Low OtG voltage range (bit #2 of Reg. 0x34 High)
Such issue is driving me nuts.
Could you please enumerate all the conditions on which such En_OtG bit will be cleared when OtG operation is attempted?
I know of some possibilities:
1) OtG_OVP & OtG_UVP (bits [1:0] of Reg. 0x20). I know definitively that there's no OVP as the adapter side doesn't rise at all, but I don't know about UVP. At what point upon enabling OtG is a UV condition declared? Does it start switching for a few milliseconds and if it hasn't risen to a given point it quits and disables En_OtG? I can't see any switching attempt nor battery current draw burst when I set the OtG pin high.
2) I know that the battery voltage cannot exceed the the Charge Voltage Register by more than 2% so that there be no Battery OVP condition which would inhibit OtG operation. I set the Charge Voltage Register to 8.856V yet I have the battery voltage at 8.2V so there's no risk of OVP tripping whatsoever.
3) I have ILim_HiZ being driven to 1.2V (for initial 500mA limiting) via a 175.1KΩ(Top)/100KΩ(Bot) divider powered from the TPS65987D's LDO_3V3 output. I confirmed I indeed have 1.2V.
Again, please kindly provide me with all the conditions that may cause the En_OtG bit to autoclear so I may troubleshoot accordingly.
Most Grateful,
Georg A. Mussenden