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TPS7H1101 current sense clarification

Carson Baisden
Prodigy 20 points
Other Parts Discussed in Thread: TPS7H1101-SP

I am looking for clarification on the current sense and programmable current limit options for the TPS7H1101-SP linear regulator. Between the datasheet and application note, I have come across numerous values for the scaling factor of Ics/Iout. 47394 is in the table, 49917 is in the text and plot of the eval board documentation, then another plot on the datasheet shows three curve providing 48065, 47935, 48150. I understand there is some variability from part to part and operating conditions. The datasheet on pp. 19 discusses PCL and uses a CSR value of 47394 for this calculation. But defines CSR as Ics/Iout. Wouldn't we want Ipcl/Iout, why is CSR defined in this calculation with Ics? Is Ics/Iout and Ipcl/Iout the same? For the high side current sense section on pp. 20. The equation uses the same CSR and a Voffset. But Voffset is in amps, just want to clarify this is really an Ioffset. Also, it appears the Ics offset is 5uA, which would correspond to 0.237 A (5uA * 47394), not 0.1899 A in the datasheet. Could you help clarify the value of Ics/Iout and Ipcl/Iout and the appropriate offsets?

TPS7H1101.pdf
  • 0
    Prodigy 30 points

    I would like to answers to these questions as well.  Also, note that the datasheet minimum value for CSR is a larger number than the one in the "nominal" column.

  • 0 in reply to Phillips Smith
    Prodigy 10 points

    I would also like to know the correct CSR min, nom, and max values.  There is an error in the data sheet as mentioned above. Elsewhere in this forum it is mentioned that CSR nominal is 47500.  Are the min and  the nom just switched in the data sheet? - Thanks.

  • 0 in reply to Steve Wood29
    TI__Expert 7445 points
    Hi Carson,

    You are correct on the electrical table for CSR will be fixed to indicated that min value is 47394, typical value 47500 and max value 56000. as there was a typo and min and typ values were switched. As highlighted Current sense ratio (CSR) has wide variation, thus one can actually measure the CSR for the device in use. CSR is ratio of output current to sense current.
    PCL ( programmable current limit) equation 8 uses CSR in the equation, however PCL current can be used. For all intensive purposes the difference between CSR and PCL current will be insignificant.
    Yes offset is in Amp and we will update the datasheet to clarify it.
    With regards to your question on offset: Per Fig. 17 which highlights 5uA offset and CSR of 49917 that gives an offset of 0.2466A , now if we take another device that may give an offset of 0.1899A thus it is variation from device to device.

    I hope I have answered your questions to your satisfaction. If so please verify the post.

    Thanks