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Original question:

TPS25750: Charger

TPS25750: Charger Compatibility and Possible Customization App Bug

Filip Lupas
Prodigy 20 points
Part Number: TPS25750
Other Parts Discussed in Thread: BQ25730, BQ25731, , PMP41013, TPS56339, BQ25792

Hello,

I want to develop an application using the TPS25750 and the BQ25730. I am fully aware that the official compatibility is only with BQ25731 so I tried using the customization app with that setting and see what I get out. 

Unfortunately when I select the BQ25731, I cannot select a lower voltage for the battery charging than 9.2V, but the charger is compatible with 1S cells, so I expect I could select 4.2V as the charging voltage. Am I missing something?

Regarding compatibility with the BQ25730: 
Is the TPS25750 ever checking the charger ID too? Both chargers have the same I2C slave address, but different charger IDs. 

Package/pin wise, the BQ25730 and BQ25731 are identical with the only difference being that the BQ25730 has power path and a pin to drive the power path FET. They have the same package and pinout where the mosfet driver pin is just NC on the BQ25731. Could I assume that if one would not care about the power path functionality, the BQ25730/1 are fully interchangeable?

The registers appear to be such constructed that what is implemented on the BQ25730 for power path, is reserved on the BQ25731, so software developed for the non power path BQ25731 version will work exactly the same on the power path version BQ25730, with default power path parameters (as a matter of fact it seems that the RESERVED bits in all the BQ25731's registers have the values such that they correspond to the default values in the BQ25730). This was done by side-by-side comparing the two datasheets register mapping and register descriptions. Am I correct in my assumption that software written for BQ25731 is directly compatible with BQ25730?

Thank you and Best Regards,
Filip-Razvan Lupas. 


  • 0
    TI__Expert 8320 points

    TPS25750 doesn't check for charger ID. Solution assumes proper BQ device is used at design. We will look into other questions you have and get back to you.

  • 0 in reply to Ghouse Mohiuddin23
    TI__Mastermind 36106 points

    Hello Filip,

    Filip Lupas said:
    Unfortunately when I select the BQ25731, I cannot select a lower voltage for the battery charging than 9.2V, but the charger is compatible with 1S cells, so I expect I could select 4.2V as the charging voltage. Am I missing something?

    This is a bug in the GUI, and is currently being evaluated, another customer has also had the same issue GUI BUG, and a fellow team member was able to create a manual workaround, to resolve it in the meantime. I can check and see if we can do this for you if that is what you want to do in the meantime. Can you export the settings and provide it here and also provide the desired values for the BQ25730? Charging voltage and current?

    Filip Lupas said:
    Could I assume that if one would not care about the power path functionality, the BQ25730/1 are fully interchangeable?
    Filip Lupas said:
    Am I correct in my assumption that software written for BQ25731 is directly compatible with BQ25730?

    I don't see any obvious issue with using the BQ25730 instead of the BQ25731, A previous customer was able to use to swap the BQ25731 for the BQ25730,

    Similar Question, and did not have an issue.

    Best Regards,

    Christian.

  • 0 in reply to Christian Moyer
    Prodigy 20 points

    Hello Christian,
    Thanks for the response and sorry for the late reply. I was to some degree aware of the workaround from that post, but wanted to know if there was any progress from that point or if I still need to reach out for a manual generation of the configuration file.
    As the specification definition is not finalized yet, I am still to define the settings, but will add them to a subsequent post on this thread as soon as possible, or should I send that request somewhere else and close this thread? 

    I wanted to make sure that if the GUI Bug is still present, there is still some way in which I can get a custom config file with a 4.2V charge voltage. 

    Thank you and Best Regards,
    Filip. 

  • 0 in reply to Filip Lupas
    TI__Expert 8320 points

    TI US was closed Sep 4th, please expect some delays.

  • 0 in reply to Ghouse Mohiuddin23
    TI__Mastermind 36106 points

    Hello Filip,

    I spoke with an expert on this issue, and was informed that this is not a bug in the GUI. This is an issue with the TPS25750 device. The TPS25750 has a hardware limitation that prevents it from setting the charge voltage to below 9.2V,  because of this issue I can not create a manual workaround. 

    Best Regards,

    Christian.

  • 0 in reply to Christian Moyer
    Prodigy 20 points

    Hello Christian,

    Surely this cannot or shouldn't be a hardware issue with the TPS25750 as there is only communication with the charger which I would assume uses a generic I2C interface, and if by hardware limitation you mean the PP5V UVLO, that won't be relevant as the TPS25750 is attached to a UFP/Sink-only port, and PP5V doesn't need power when there is no VBUS present (which I think is the case for which you/your colleague say it is not possible). This limitation is also very specific (it seems) to the specific hardware configuration of the PMP41013 reference circuit. 

    As a validation check, considering the  PMP41013 Buck converter (TPS56339) Powering PP5V from the battery pack, if that was changed to a Buck-Boost Converter for a true bidirectional operation from 1S-5S packs, would this limitation still exist (never-mind the practicality, just as a concept)? 

    It would be very helpful to get a confirmation that we can still use the method in  GUI BUG to get a custom config file, as otherwise there is less incentive to use the part. 

    Thank you and Best Regards,
    Filip. 

  • 0 in reply to Filip Lupas
    TI__Mastermind 36106 points

    Hello Filip,

    I spoke with the expert again and he confirmed that it is a hardware/firmware issue that requires the minimum charge voltage to be set to 9.2V, We are currently looking into the issue, but at this time we do not have a timeframe on when this issue will be resolved. I can provide you with an update when I get more information. I spoke with the person that create the manual work around, and he said that it is not recommend because it is a difficult process that could lead to futher issues.

    Best Regards,

    Christian

  • 0 in reply to Christian Moyer
    Prodigy 20 points

    Hello Christian,
    Thank you for the quick follow-up. 
    One last question then, if I instead use the bq25792 where in the TPS25750 Application there is no such limitation (can set 4.2V output) but based on your explanation this is an issue with the TPS25750 instead, is that 9.2V limitation carried over, but just not highlighted in the App? 

    Best Regards,
    Filip. 

  • 0 in reply to Filip Lupas
    TI__Mastermind 36106 points

    Hello Filip,

    Filip Lupas said:
    One last question then, if I instead use the bq25792 where in the TPS25750 Application there is no such limitation (can set 4.2V output) but based on your explanation this is an issue with the TPS25750 instead, is that 9.2V limitation carried over, but just not highlighted in the App? 

    I'm looking into this issue and will provide you with an update when I get more information.

    Best Regards,

    Christian.

  • +1 in reply to Christian Moyer
    TI__Mastermind 36106 points

    Hello Filip,

    I apologize for the confusion. The hardware/firmware issue that my colleague mentioned involves the TPS25750 attached to a DFP/Source port. There is also a GUI bug that prevents the charge voltage being set below 9.2V when the TPS25750 is attached to a UFP/Sink-only port and BQ25731 is selected. The GUI bug is currently being looked into, but as of this time I do not have a time frame on when this GUI bug will be resolved.

    Filip Lupas said:
    One last question then, if I instead use the bq25792 where in the TPS25750 Application there is no such limitation (can set 4.2V output) but based on your explanation this is an issue with the TPS25750 instead, is that 9.2V limitation carried over, but just not highlighted in the App? 

    Yes, You should be able to use the TPS25750/BQ25792 with an output of 4.2V, becasue this is a GUI issue with the TPS25750/BQ25731

    Best Regards,

    Christian.