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TIDA-050047: BQ25792

Prodigy 240 points

Replies: 10

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Part Number: TIDA-050047

I am building a product that requires USB-C charging of 3 cell battery, 12.6V 4A fast charge.
I am interested in using BQ25792 + TPS25750D as shown in TIDA-050047. I would appreciate some support with the following queries:

1) For sink only application I am expecting to not need TLV75533 (U2) or TPS54531 (U3).

2) What is USB2ANY Header (J3) used for? Do I need this?

3) Should I connect JP4 in my design for TS?

4) Can you provide further information about how an external thermistor should be interfaced with BQ25792. Section 8.3.9.5.1 of the BQ25792 datasheet contains formula for calculating RT1 and RT2 however I cannot make the figures align for the example presented where RT1 and RT2 are calculated to be 5.24KΩ and 30.31KΩ.

5) If I remove TLV75533 (U2) and TPS54531 (U3) and possibly J3, will this design be sufficient for charging up to 4A?

6) Is TIDA-050054 capable of charging up to 5A?

7) Also, please provide any key PCB layout information to ensure my design will operate without issues.. Track width, isolation etc.

Many thanks

  • Question no. 6 should TIDA-050047.

  • Hi Kiran,

    1. For sink-only applications, yes, you may omit the 5V and 3.3V power supplies.

    2. The USB2ANY header is used for further internal debug of the battery charger, you may omit this as well if you would like. 

    3. Yes you should connect JP4 for the normal thermistor option.  could you please answer question 4 regarding the external thermistor?

    5. Without those components, yes you will still be able to charge at 4A as a Sink-only device.

    6. Yes this design is capable of charging up to 5A but I would recommend making sure the thermal regulation will not be an issue and properly sizing the layout.

    7. You may reference the TPS25750 datasheet and the BQ25792 datasheet, specifically the Layout sections for detailed information on layout sizing and recommendations.

    Thank you,

    Hari

  • In reply to Hari Patel1:

    Thanks for your reply Hari.

    Regarding thermistor, I will await Michael Emanual35

    8. For question 6, what is the temperature rise pm TPS2750 and BQ25792 expected from TIDA-050047?
    I will refer to layout guidelines for more details.

    9. TPS25750 contains thermal pad and datasheet parameter Rpphv can be used to calculated power dissipation. Does thermal resistance specified in datasheet section 7.5.1 assume thermal pads are soldered? What are the assumptions about copper thickness?

    10. BQ25792 datasheet Section 7.4 specifies thermal resistance, what are the assumptions about copper thickness?

    Thanks

    Kiran

  • In reply to RMRM1:

    Dear Kiran,

    Connecting JP4 will bias the TS pin in normal operation. Specifically, the TS pin will be 58.9% of REGN and this will bias the charger will full charge current and full charge voltage because it will be between the T2 and T3 windows.

    The first step for the TS calculation is to calculate the desired temperature range that VT1 and VT5 will correspond to.

    For the calculation, please make sure that the voltages used, ie VT1 and VT5, are expressed as ratios of REGN. In other words, these values should not be voltages but rather ratios. Please refer to page 16 of the BQ25792 datasheet to see how these values are expressed as ratios of REGN. These percentages are specified as Electrical Characteristics.

    RTH_HOT and RTH_COLD are the values your thermistor will have for resistance at the desired temperature cutoffs that correspond to VT1 and VT5.

    Use VT1, VT5, RTH_HOT and RTH_COLD to calculate the upper and lower resistance values required to achieve the desired temperature range.

    Thanks,

    Mike Emanuel

  • In reply to Michael Emanuel35:

    Thanks Mike.

    I will await Hari's response to my final questions.

    Also, One last question,

    11. We are considering to use a 2 layer PCB for our design, would this be an issue for our application where we will not be looking to exchange USB Hi-speed data? All we want to do is negotiate power contract and charge battery.

    Regards

    Kiran

  • In reply to Kiran Kerai:

    Dear Kiran,

    Tight placement of the BQ25792 SYS and PMID Capacitors is achieved through routing the SWx through an inner PCB layer. We have not tested the BQ25792 on a 2-layer board yet. Please see the attached E2E post.

    Thanks,

    Mike Emanuel

  • In reply to Michael Emanuel35:

    Thanks very much for your help!

    I have a few more questions:

    1) I2C1 slave interface to U4 pin 8 and 9 are connected to USB2ANY (J3) which I do not intend to fit in our design. However, if we want to use external MCU to program then I assume we will need to connect via pin 8 and 9?

    2) To facilitate MCU host loading of configuration, can the Application Customization tool be used to retrieve data required to be transmitted by MCU? Does the application allow binary to be extracted?

    3) From Table 9-5 with ADCIN1 and ADCIN2 at 1V5, can you confirm this will be decoded as ADCIN1=3, ADCIN2=3 and therefore device will be configured to NegotiateHighVoltage?

    4) I have removed PP5V connection to TPS25750 as we are using for sink only application. We will be powering via PPHV at all times. Please confirm this is ok.

    Regards

    Kiran

  • In reply to Kiran Kerai:

    Hi Kiran,

    I will look into the first 2 questions and get back to you later this week. 

    For 3, I believe connecting them both to LDO_1v5 will select the configuration AlwaysEnableSink but I can confirm with you on that.

    For 4, if you are sink only, you won't need PP5V or VIN_3V3, however, if you would like to have the PD controller to be powered on and not in dead battery mode, you will need to power via VIN_3V3 not PPHV.

    Also, if you have additional questions, I would recommend creating new e2e threads.

    Thank you,

    Hari

  • In reply to Hari Patel1:

    Thanks Hari

    I look forward to your final responses and will open a new thread if I have any more questions.

    Regards

    Kiran

  • In reply to Kiran Kerai:

    Hi Kiran,

    For your I2C1 question, yes you will need to connect to pins 8 and 9 similar to the guide.

    As far as the application Web-GUI goes, yes you can download the binary directly from there based on your selected configurations.

    Thank you,

    Hari