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BQ25713: HIDRV pin not zero when no DC input is attached

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Replies: 17

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Part Number: BQ25713

Hi forum, 

Thank you in advance for your time. 

My design with BQ25713 encounters an issue. When there is only battery attached to the system and no register is set, I measured a voltage at HIDRV1 and HIDRV2 with behavior as shown in Figure 1.    

With no DC input connected, the same voltage is transferred to Vbus which caused the charge status reg to show Adapter Present. 

If I uncheck the EN_LWPWR, disabling the low power mode, HIDRV1 and HIDRV2's behavior change to as shown in Figure 2 and Figure 3. 

  Figure 1 HIDRV1 and HIDRV2 with only battery attached

        Figure 2 and 3, HIDRV1 and HIDRV2 reset period change from 3.58s to 5.24s for different PCBs. 

If I enable HIZ mode, the voltage on HIDRV and Vbus stays around 3.5V. 

Comparing to EVM, HIDRV and VBUS should be zero when there is no DC input. 

I also attached the screen capture of my schematic and layout. 

Please feel free to ask if you spot any error or need more information. 

Thank you

Jerry 

  • In reply to Shishuo Zhao:

    Hi Shitshuo, 

    Is there any update on the issue?

    I have 2 designs with BQ25713, one with number AG4J on the package which works fine. the other one is AE61. 

    I dont know if the serial number has any connection with the malfunctioning.

    Would this issue cause by assembly? 

    Looking forward to your reply. 

    thank you 

    Jerry  

  • In reply to jerry liang:

    Hi Jerry:
       

         From the waveform, it looks like your HIDRV1 is just any offset 1V offset adding over the SW1 which means that you HIDRV1 is not driving normally. Do you try to replace a new part to see if this issue consistent? You may also need to replace the FETs also.

    Regard

    Shishuo

  • In reply to Shishuo Zhao:

    Hi Shishuo, 

    Sorry for the confusion on the photo i provided. There is no offset between SW1(purple) and HIDRV1(green) if you look at the CH3 high and CH4 high on the right side. 

    I offset the display so I can show you both of the waveforms.  

    I have not replace any part since it is very difficult for this packaging with the thermal pad below. 

    Thank you 

    Jerry 

  • In reply to jerry liang:

    Hi Shishuo, 

    Just want to do some update. I replaced the part but the problem persist. 

    It seems to be there is some charge accumulated over the path to cause the voltage build up at the input. 

    I place a 10k ohm resistor to between the input and ground, the voltage drops to 0.8V stable, as well as HIDRV1, VDDA is not being turned on. 

    The accumulated current is about 80~50uA, Does this value ring any bell?

    Best regards, 

    Jerry  

  • In reply to jerry liang:

    Hi Jerry:
        

        Thanks for letting me know. Do you have any other silicon on the system besides our BQ25710? I am trying to figure out the leakage current source. Under low power mode(disable HIDRV1 and VDDA), our part should not contribute any leakage current you mentioned as charge accumulation. Thanks.

    Regards

    Shishuo

  • In reply to Shishuo Zhao:

    Hi Shishuo, 

    There is no other IC besides BQ25713. In fact, I only connect one diode to the output of BQ25713 which ensures nothing flows backward, and the charge accumulation persists.

    Under low power mode, HIDRV1 should not be on at all. The only time I have seen HIDRV1 and HIDRV2 on are pass-through mode, but the IC does not power up in PTM neither. 

    What I observe at start up is that the input voltage first rises up, then the VDDA starts to turn on and HIDRVs begins to toggle. 

    last, I set BQ25713 in HIZ mode in my previous PCB which works fine, HIDRV1 and HIDRV2 is 1V, the input stays at around 1V as well. 

    But in the new version, HIDRV and input quickly rise to 5V and 7V respectively. 

    Hope this HIZ comparison would give you more information. 

    So far, I had

    1. replace the IC but the issue persists,

    2. compared the schematic and layout of both functioning and malfunctioning version of PCB,

    3. probe the resistance on both versions of PCBA and bare PCB respectively but found no short, open or big discrepancy 

    Do you think if there one or more peripheral capacitors/resistor with wrong value would cause this issue?  

    Thank you 

    Jerry 

  • In reply to Shishuo Zhao:

    HI Shishuo, 

    Finally, I found there is a protection diode at the very beginning of the the PCB, it has a 1mA reverse current. 

    By replacing that diode, it fixed the issue. 

    Thank you for your help, much appreciated. 

    Jerry  

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