data/text/DLP4/900346

BQ25155: TS pin accidentally left floating instead of GND when we don't plan to use it

Part Number: BQ25155 Hi, in the latest revision of our product, we accidentally left TS pin floating and the battery management started to behave strangely. When no battery is inserted and we plug in USB to power up the VIN, the MR pin quickly goes up and then falls to the low, which means that the device won't boot because it is in the reset state. However, when we plug in the battery and USB, everything works as expected. All power rails all good no matter if the battery is inserted or not. The MR pin is weird only without the battery and we hadn't this trouble in the last revision where we had the TS pin grounded. I suppose that the TS pin needs to be grounded to be able to operate the BQ25155 without a battery. Could you please confirm this information? Best regards, Lukas

Hello, The /MR pin is pulled up to VBAT and since the battery is absent, you'll see the capacitor on battery pin get charged and discharged. This will also be seen on /MR. The VDD and PMID pins should be powered when on VIN plugin only.

Hi, > The /MR pin is pulled up to VBAT and since the battery is absent, you'll see the capacitor on battery pin get charged and discharged Yeah, this is the expected behavior we saw on our previous revisions. The /MR was oscillating between 1.5 and 4.2 V. But we have now new revision, where we forget to ground the TS pin, and when the battery is removed the /MR is permanently pulled low (not oscillating). Could you please confirm this could be caused by TS pin grounded? Thanks, Lukas

Hello, Can you share your schematic? What is VDD and PMID voltage when you have only VIN present? If you can write to the registers, can you try disabling the TS function and see if the behavior changes?