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BQ25606: BQ25606 charger input short to ground

Part Number: BQ25606

Hi

The customer design the schematic with BQ25606, found the input terminal short and had no abnormal appearance, after changing the chip, the issue was fixed. One of them can be seen that the output terminal of the charging chip has burnt black marks.

The schematic as below:

They use 9V adapter, what kind of problems can cause this phenomenon?

Waiting for your reply.

Thanks

Star

  • Star,

    1. Which pins of the BQ25606 device were damaged?

    2. There are two BQ25606 devices on the schematic. Which device was damaged?

    Thanks,

    Ning.

  • Hi Ning

    Thanks for your reply.

    Both will be damaged, not necessarily, the result is that the burned chip VBUS is shorted to ground.

    We do the test was repeated plug ig and plug out the adapter, and repeated plug in and plug out the battery, but it did not recur.

    I want to know what may cause this bad.

    Thanks

    Star

  • Star,

    If the 9V adaptor supports only one BQ25606 charger instead of two BQ25606 chargers, will the VBUS pin be OK?

    Thanks,

    Ning.

  • Hi Ning

    Thanks for your reply.

    This failure samples is end user fail return to customer side, and they want to duplicate the same phenomenon.

    The customer do some test and want to know whether the tests will cause a short circuit between VBUS and ground.

    1, At the beginning of charging, one of device will work and charge about 2S.  During operation, the battery voltage will switch between 2.5V and 3.8V with the working frequency of the device, and the current will also be Glitch. The test waveform is as follows, blue is the battery voltage, yellow is the charging current.

    2, When plug in and plug out the adapter, the adapter has a spike of 20A. At this time, the battery has not started charging. Does this affect the chip?

    Waiting for your reply.

    Thanks

    Star

  • Star,

    1. It is strange that the battery voltage will switch between 2.5V and 3.8V. Is it real battery under testing?

    2. 20A is too high for the charger.

    Please test with only one charger alone and check if the operations are normal.

    Thanks,

    Ning.

  • In this case, only one charger is work, the battery is assembled in the equipment when the battery charging , at the same time the equipment is working ,  so the battery is discharging at the same time, the duty cycle is about 20ms,when the duty on,for the discharging current is large,   the battery voltage will drop to 2.5V, when the duty off, the battery voltage will change to 3.8V,so the voltage  will switch between 2.5V and 3.8V . I wonder if it's can cause VBUS short with GND.

    I test one of the fail IC, and find VBUS, PMID,REGN,BTST,SW  all short with GND

    I wonder what can cause this pins short with GND, in this way I can reappear the failure phenomenon, and know how to optimize the design.

  • Hi,

    BQ25606 is 3-A charger. The recommended battery discharge current is no more than 6-A. Too high battery discharge current may damage the BAT pin, the SYS pin, the BATFET... When SYS pin is short to GND, high input current could be demanded from VBUS which may damage the VBUS pin and other pins on the power path. Please avoid stresses on the charger beyond the recommended and absolute max ratings listed on the d/s.

    Thanks,

    Ning.

  • But pin BAT is not dameged, the resistance between pin BAT and GND is 6Mohms, same as normal IC,  Is the failure caused by the abnormal operation from VBUS(ESD??  inrush current?)  Today,I short  pin VBAT  with GND frequently,  I think it's the worst case,but the charger still can work normal,

  • SYS not connetct to load in the design, pin BAT connect to the loads, both charging,discharging  are form pin BAT

  • Hi,

    We will get back to you on the next business day.

    Thanks,

    Ning.

  • Hi

    Could you give me any seguestion about the design?

  • Hi,

    As stated earlier, BQ25606 is 3-A charger. The recommended battery discharge current is no more than 6-A and the recommended input current is no more than 3.2-A. 20-A current spike is much higher than the recommended and absolute max ratings listed on the d/s. Please improve the custom system design and PCB design so that the device will not be stressed over the specified limits during operations to avoid device failures.

    Please visit https://e2e.ti.com/support/power-management/f/196/t/890626 for BQ25606: Schematic Review and PCB Layout Design Tips. Additional Information including FAQs is available http://www.ti.com/lit/an/slva924/slva924.pdf Designing A Standalone Single Cell 3-A Charger with the bq25606.

    Please contact the local support team for detailed explanations and further support.

     

    Thanks,

    Ning.

  • I want to know if  pin VBAT  with GND, Will it cause the IC damaged?

  • Hi,

    It is ok for the BAT pin voltage to be 0V and the device will charge at 90mA typically. But if connecting the BAT pin to GND causes overcurrent/overvoltage conditions (i.e. beyond absolute maximum current/voltage specs), the IC could be damaged.

    Thanks,

    Ning.