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TPS1H100-Q1: TPS1H100-Q1 - Query on current limit

Sri Viswa S
Prodigy 120 points
Part Number: TPS1H100-Q1

Hi,

The part number used is TPS1H100AQPWPRQ1. The set current limit is 0.62A. The current in the design may go upto 702mA. During that period, the current limit kicks in and maintains the current upto 0.62A. WIth

0.62A, the junction temperature of the high side switch is calculated as 105C when the ambient is 95C. This current limit may remain for a long time. Whether this will cause any issue? It seems junction temperature is

well below the rated junction temperature. 

Thanks

Viswa

  • 0
    TI__Genius 13300 points

    Hello Sri,

    The nominal current range for the TPS1H100 device is 0 to 4 A. The current sense accuracy will be +/- 5% for your case. 

    T_J = T_A +((I_LOAD^2∗R_ON)∗R_ΘJA)

    95 + ((0.62^2*0.166)*41) = 97.62C

    T_J is well below the limit, just as you've said, so there won't be issues. If you need more information on driving resistive loads please look here:

    How To Drive Resistive, Inductive, Capacitive, and Lighting Loads (Rev. B)

    Regards,

    Kalin Burnside

  • 0 in reply to Kalin Burnside
    Prodigy 120 points

    Hi Kalin,

    Thanks for your reply

    In the datasheet, page no:7, note 4 is given as 

    "External current-limit setting is recommended to be higher than 500 mA." Is there any specific reason, this recommendation was given? What will be effect if external current limit is set below 500mA?

    Thanks,

    Viswa

  • 0 in reply to Sri Viswa S
    TI__Genius 13300 points

    Hello Sri, 

    You're welcome.

    The reason it is recommended to be higher than 500 mA is due to the accuracy of the current limit. If you go below 500 mA the accuracy is worse than +/- 20% which is indicated in the electrical characteristics on page 7 of the datasheet. 

    Regards,

    Kalin Burnside

  • 0 in reply to Kalin Burnside
    Prodigy 120 points

    Hi Kalin,

    It is also mentioned that the external current limit accuracy is only applicable to the overload conditions greater than 1.5 times the current limit setting.

    So if the current limit is set to 485mA, and the current in design is less than (1.5 x 485mA), then it is not needed to use the accuracy right?

    During short circuit conditions, the current value will increase above (1.5 x 485mA). In that case, I think accuracy is important. 

    Correct me if I am wrong

    Can you provide the approximate (if exact data is not available) accuracy for current limit less than 500mA?

    Thanks

    Viswa

  • 0 in reply to Sri Viswa S
    TI__Genius 13300 points

    Hello Sri,

    An overload condition must occur for the current limit to take effect. In order to get the datasheet accuracy for this part at 500 mA (+/- 20%) you must have an overload condition that is at least 1.5x the current limit set, otherwise the accuracy of the datasheet is not guaranteed. If you are looking to set the current limit below 500 mA I would suggest using a different device such as the TPS1H000.

    TPS1H000-Q1 40-V, 1-Ω, Single-Channel Smart High-Side Switch datasheet (Rev. C)

    Regards,

    Kalin Burnside