BQ25306: the charge current not stable when battery near to full, and cause unstable VBUS ripple

Hi,

   Can you capture charge current, VPMID, VBAT and load current when battery is near full charge? Is the part already in CV when a load is added to the battery? The part has a recharge threshold which will trigger a new charge cycle if battery dips below VRECHG. Can they try the full charge cycle without adding this extra load?

HI Kedar,

upload customer's test data here. can you give comment.

XEL5 展台样机 低概率 出现杂音——BQ25306充电IC环路不稳.xlsx

HI Kedar,

can you tell me how to choose the feedforward cap value, what is the side effect if remove it?

Hi Kedar,

thanks for your reply,

if regards to loop stability, I think we can test the loop gain and phase on customer board since the loop stability not only related to the feedforward capacitor but also related to parasitic of the board. in my observation the feedforward capacity on customer's board just cause the oscillation.

here is loop test on customer board with and without 470pF feedforward cap.

loop test happened under the CV mode.

with 470pF cap:

without 470pF cap.

can you provide your comment on this case?

Thanks.

Anderson

Hi Anderson,

   From the results it looks like the customer's board happens to be more stable without addition of the 470pF external feedforward capacitor. Do you see any oscillation when removing the feedforward capacitor? 470pF creates stability on EVM but customer board parasitic look different and 470pF should be able to be removed, to remove oscillation.