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wide control and input range buck converter

Robert Muniz
Prodigy 70 points
Other Parts Discussed in Thread: TPS65987, TPS55288, TPS65987D, LM3489

Application is for a buck converter to power a USB-C PD 100W system. Need for the controller to be switchable over the full range, 5V to 20V the standard addresses.

Hysteretic controllers I see (which I assume address the control range issue while remaining stable) appear to have narrow input voltage range. I need as wide an input voltage range as practical.

I'd also like to know the operational extremes of the TPS65987 as these are not outlined in the documentation that I see. Specifically the minimum boot voltage and current, minimum idle current and voltage and maximum voltage. The worse case chip is rated for 30V though the documentation specifies 20V. I need to know if that is a hard limit for other reason than IC over voltage.

Thanks.

  • 0
    TI__Genius 12700 points

    Hi Robert,

    I've assigned this issue to the relevant expert who will get back to you shortly.

    Thank you,

    Hari

  • 0 in reply to Hari Patel1
    TI__Mastermind 30000 points

    Hi Robert,

    The best DCDC that I can recommend that has a large voltage input range is the TPS55288. You can reach out to the team responsible for that device is you have specific questions. You would post a new question with the TPS55288 as the part you reference. This will assign it to the correct team.

    As far as the power consumption of the TPS65987D and the maximum pin tolerance of PPHV and VBUS, both of these measurements can be found in the datasheet. 

  • 0 in reply to Adam Mc Gaffin
    Prodigy 70 points

    Hi Adam,

    I apologize as my original post was not clear:

    I'd like to know the operational extremes of the TPS65987 Evaluation Module. Specifically:

    the minimum boot voltage and current: Conditions where the board wakes up and starts communicating albeit not necessarily able to produce power.

    minimum idle current and voltage: condition where the system is fully functional and able to deliver power.

    maximum input voltage: the worse case chip on that board is rated for 30V though the documentation specifies 20V as a maximum voltage for that board. I need to know if that is a hard limit for other reason than the worse case IC over voltages.

    Re the supply:

    The TPS55288 you recommend is a fair option for my 100W USBC-PD application. Expanding on that part, it is notable that the output voltage is selectable through I2C. Is this part designed such that, over the full load range, output voltage range and input voltage range, with any combination of extremes within its rating, it remains stable with a single control loop value set?

    Alternately, a second approach for my USBC-PD application is to limit the input voltage to >20V so I can maintain buck operation. The hysteric control of the LM3489 seems desirable to accommodate the output load and voltage range but it lacks synchronous rectifier and is limited to 30V. I can get around the latter by using an external sense resistor (correct?); otherwise my input voltage might go as high as 60-70V. In this context, wide input voltage refers to the upper end above a mx OP voltage (20V). For a full range USBC-PD application, does TI offer other hysteretic controllers that address my concerns?

    Are there other parts, ignoring other limitations, designed for use in USBC-PD applications?

    Thanks,

    ~Bob

  • 0 in reply to Robert Muniz
    TI__Mastermind 30000 points

    The TPS65987EVM uses a 19.5V barrel jack connection to power the entire system. If you do not have such a barrel jack, you can use an external bench supply programmed to 19.5V or 20V. This is what we recommend for powering the EVM for evaluation purposes.

    There is no data available showing the minimum current to power the entire system since a customer will use an external bench or barrel jack to supply power to the EVM. 

    If your input voltage can go as high as 70V, you cannot use the LM3489 or the TPS55288. I would recommend using the WEBBENCH tool and put in your requirements to pull up the full list of potential devices. You can find a device that uses a feedback pin similar to the LM3489, and implement a series of external FETs controlled by the TPS65987D connected to the feedback pin of the DCDC to control the output voltage. I cannot offer any more assistance on this topic though since I am not an expert on these devices, only the TPS65987D. If you have a new question about any of the DCDCs post your question in a new E2E thread, and reference the DCDC that you have a question over. This will assign it to the correct people. 

  • 0 in reply to Adam Mc Gaffin
    Prodigy 70 points

    Did NOT resolve issue. "No data available" from the manufacturer seems unlikely.

    "since a customer will use an external bench or barrel jack to supply power to the EVM." I am proposing NOT using a barrel jack but I can not expound without and NDA in place. Who do I speak with in order to get an NDA in place so I can discuss my specific requirements in greater detail?

  • 0 in reply to Robert Muniz
    TI__Mastermind 30000 points

    Hi Robert,

    I worked alongside with the engineers that developed the TPS65987EVM, and performed the testing/validation of this EVM. I can confirm that we do not have any data available about the total power consumption of the TPS65987EVM. This is because the purpose of the TPS65987EVM is to allow customers to evaluate the TPS65987D. The TPS65987EVM is not a stand alone product, but instead an evaluation tool that will be used in a lab environment where power consumption is not an issue. 

    I do not believe there is a need for an NDA. The TPS65987EVM is not a standalone product, so you should not treat it as such. It is a tool used to evaluate the TPS65987D to then populate onto your system/hardware. 

  • 0 in reply to Adam Mc Gaffin
    Prodigy 70 points

    Hi Adam,

    To be clear, I have not requested nor am in need of total power consumption.

    Allow me to distill my requirements to the absolute minimum of that originally requested:

    1-Minimum boot voltage of the TPS65987EVM: What is the lowest voltage the EVM will boot up. 

    2-Maximum voltage tolerance.

    As you were part of the validation/testing of this EVM, surly these basic parameters are known and documented? If these two operational parameters are not documented, how difficult would it be to put one on a bench supply and simply measure these 2 parameters?

    Re NDA: As I am under a confidentiality agreement with my client, all I am at liberty to say is the NDA request extends to system level discussion and support hardware extending beyond the TPS65987 and EVM. I understand you are not in a position to assist in the matter of a corporate level NDA and will pursue other channels. Thanks for your input on the matter.

    Thanks for all fo your help so far!

    Regards,

    Bob Muniz

    harmonic-power.com

  • 0 in reply to Robert Muniz
    TI__Mastermind 30000 points

    The EVM requires 19.5V or 20V. You cannot apply more or less voltage as the system was not designed for that. Once again, the TPS65987EVM is a evaluation tool and has only one input voltage level. This is provided via the barrel jack connection or an external bench supply connected to the SYS_PWR test point.