• State Resolved
  • Locked Locked
  • Replies 9 replies
  • Answers 2 answers
  • Subscribers 63 subscribers
  • Views 485 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Original question:

BQ25890: the VSYS transient voltage drop is lower than 3V

BQ25895: Source Detection vs Vsys

Mike Yu
Intellectual 2390 points
Part Number: BQ25895


Hi Team,

Ref to BQ25895, we found that the Vsys will dip whenever we do a "force Vin detection" with the EVB.

 

Step to repro:

  1. Connect Vbatt to 2.4V
  2. Connect Vin to CDP
  3. Select "Force Vin Detection" with the BQ EVB GUI.

Below is the Vsys signal.

Sorry, not very well captured, but the top is 3.5V (default Vsys value). Dip is ~2.4V, the Vbatt value.

 

The Vin source is CDP.

I think the Vsys source is switched from Vbus to Vbatt during source detection that cause the dip.

 

If so, are there any situation beside doing source detection that will cause this switching?

What other sources will have this switching beside CDP?

Best regards,

Mike

  • 0
    TI__Mastermind 32150 points

    Hi Mike, 

    We are looking into this and will get back to you. 

    Best Regards,

    Garrett 

  • 0 in reply to Garrett Kreger
    TI__Mastermind 32150 points

    Hi Mike, 

    To clarify when you say you are setting "force vin detection" are you setting REG02 bit 1 FORCE_DPDM? Following your setup then only writing to that bit I do not see the same behavior. SYS voltage remains above 3.5V. 

    Best Regards,

    Garrett 

  • 0 in reply to Garrett Kreger
    TI__Intellectual 2390 points

    Hi Garrett,

    Yes, it is REG02.1. Add one more waveform as below.

    Red is Vbus, Blue Vsys.

    Tested with Laptop CDP.

    1st dip is when plug in USB

    2nd dip is when toggled the REG02.1

     

    Can you confirm you are using CDP?

    Also Vbattery is 2.4V, i.e. much lower than Vsysmin.

    Best regards,

    Mike

  • 0 in reply to Mike Yu
    TI__Intellectual 2390 points

    Hi Garrett,

    Another more interesting issue from another laptop CDP.

    It just keep repeating the loop without having to toggle the force DPDM.

    Is this typical of CDP port to shut the Vbus for detection?

     

    In this case I can see that the port is detected as SDP, charging current is only 128mA (precharge).

    So far I don't see this with DCP.

    Best regards,

    Mike

  • 0 in reply to Mike Yu
    TI__Guru 58791 points

    Hi Mike,

    We will do some research and get back to you by next Tuesday.

    Thank you very much,

    Ning

  • 0 in reply to Ning T
    TI__Mastermind 32150 points

    Hi Mike, 

    Please see my comments below. 

    I do not have access to a laptop CDP in our lab currently. With the setup I am using my BQ25895EVM correctly detects CDP input and VBUS and SYS voltage levels do not change when I force DpDm detection with REG02 bit 1. 

    With that said I did some additional research and found the BQ25895 has a known limitation where it does not consistently detect all CDP inputs. In this case when the USB port does not see the correct response it power cycles and becomes SDP (which matches your observation). 

    It appears the BQ25895 cannot correctly detect the laptop CDP ports you are testing, which is resulting in the port power cycling and switching to SDP. When the input power cycles it is expected for SYS voltage to reduce from SYSMIN to battery voltage. 

    Best Regards,

    Garrett 

  • 0 in reply to Garrett Kreger
    TI__Intellectual 2390 points

    Hi Garrett,

    Thanks for the reply. Do you have any errata for this CDP limitations? Any possibility that the DCP (or any other source) is wrongly detected as CDP and thus encounter this issue?

    My customer reported that a depleted device encounter reset loop for few seconds. From the power meter data, it seems that 5V is cut off.

    Best regards,

    Mike

  • 0 in reply to Mike Yu
    TI__Mastermind 32150 points

    Hi Mike, 

    I do not have an errata available. The issue should only be with CDP inputs we have not had reports of issues detecting other ports such as DCP and SDP. 

    Here is a more specific description I can provided. Some CDP inputs require smart phone (i.e. system you are trying to charge) to send out enumeration within 1.3 sec (min) of adapter plug in. Otherwise the port will power cycle back to SDP. 

    The 5V input repeatedly power cycling is dictated by that specific CDP port, this power cycling is not something that can be controlled by the charger IC. 

    Best Regards,

    Garrett

  • 0 in reply to Garrett Kreger
    TI__Intellectual 2390 points

    Hi Garrett,

    Thanks for the support, let me share with customer.

    Best regards,

    Mike