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TPS2HB16-Q1: Upper and lower limits of the RSNS

TAKAHIRO HOJO
Prodigy 160 points
Part Number: TPS2HB16-Q1

Hello!

What are the upper and lower limits of the Rsns resistance that can be set for TPS2HB16?

If it is less than 1kΩ, what is the limit resistance value that can flow Isns correctly?

If it is larger than 1kΩ, what is the maximum resistance value that can be increased, except considering the effect on the MCU?

I mainly want to accurately detect a low current range of several 100mA.

Regards,

  • 0
    Prodigy 160 points

    Now I want to use Rsns of 15kΩ.

    Please check.

  • 0 in reply to TAKAHIRO HOJO
    TI__Genius 16390 points

    Hi Hojo-san,

    The max resistance is limited by the max voltage can be taken by the MCU from the ISNSFH*RSNS. In this case, the fault current is 5.3mA, with 15k resistance, the voltage is way over. 

    An alternative way to do this is using a zener diode to clamp the voltage, and the downside is you can't differentiate a high current event vs. fault situation.

    Regards,

    Yichi

  • 0 in reply to Yichi Zhang.
    Prodigy 160 points

    Hello Yichi-san,

    Zener diode or capacitor is going to be used as measures against the voltage for MCU.

    In point of view of ratings or recommendations of TPS2HB16, I want to know the upper and lower limits of the Rsns resistance.

    Is it correct that the rating of the TPS2HB16 is not exceeded by any resistance of Rsns?

    Regards,

  • +1 in reply to TAKAHIRO HOJO
    TI__Genius 16390 points

    Hi Hojo-san,

    The RSNS selection you have is fine as long as the voltage is properly clamped. There are no constraint on the RSNS value.

    Thanks!

    Regards,

    Yichi

  • 0 in reply to Yichi Zhang.
    Prodigy 160 points

    Hi Yichi-san,

    I have related questions.
    According to figure 1 of SLVAE08,is it correct that the voltage of the SNS pin is limited by VBB?
    Should measures against the voltage for MCU be done up to VBB?
    There is no description, but is the Isnsfh(4~5.3mA) in the datasheet of TPS2HB16 only for the case of Rsns of 1kΩ?
    It is impossible for 5.3mA to flow even with Rsns of 15kΩ (V = 5.3mA * 15kΩ = 79.5V), isn't it?

    Regards,

  • +1 in reply to TAKAHIRO HOJO
    TI__Genius 16390 points

    Hi Takahiro-san,

    Your understanding is correct. The max voltage possible at SNS will be close to VBB. With the 15k case, you will need to externally clamp the voltage at SNS as the SNS voltage should be under 7V, and there will be requirements from microcontroller as well. In that case, the max current output will be determined by the VSNS(clamped)/15k. Please let me know if you have additional questions.

    Regards,

    Yichi

  • 0 in reply to Yichi Zhang.
    Prodigy 160 points

    Hi Yichi-san,
    Thank you for your answers.
    I have confirmed that requirements of MCU side are satisfied.

    I have additional questions.
    Even if Rsns is 15kΩ, is the operation of TPS2HB16 guaranteed if Iout is within the Vsns recommended operating range of 7V or less in the absence of short-to-ground, noise, and surges?
    Is it acceptable for the TPS2HB16 to have Vsns rise to VBB for a short time between short-to-ground and shutdown of IC's protection?

  • 0 in reply to TAKAHIRO HOJO
    TI__Genius 16390 points

    Hi Hojo-san,

    If the voltage is below the 7V it should be fine. As the abs max for the SNS pin is 18V, as long as it doesn't exceed 18V for the short period, it should be okay.

    I would suggest customer to order an EVM and use 15k to test their operation before they make their own PCB into production.

    Please let me know if you have additional questions.

    Regards,

    Yichi