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TPS1H100-Q1: Caribration method to improve current sense accuracy

Tomoaki Yoshida91
Genius 5255 points
Part Number: TPS1H100-Q1

Hi team,

I would like to improve current sense accuracy using TPS1H100-Q1.

Therefore, I'm considring to calibrate in the system.

The target accuracy is ±1% when load current is over 200mA.

I think that I will be able to cancel the offset by storing the offset current when turning off the switch, is this effective?

If this is effective, then can I cancel the offset temperature drift?

If I know what temperature drift fwithin the range, I can multiply the offset cancellation amount by the temperature coefficient.

If this method is effective, to what extent can the accuracy be improved theoretically?

Best regards,

Tomoaki Yoshida

  • 0
    TI__Mastermind 28200 points

    Hello,

    The offset voltage on CS pin, when the switch is off, is almost 0mV. This value can not help in calibration. The accuracy on current sense is due to non linearity in current ratio K and is not due to offset with no load. The current ratio K is very stable with temperature when load current is higher than 100mA with accuracy of around 1%. Please refer to datasheet figures 25 and 26.

    Regards, Mahmoud

  • 0 in reply to Mahmoud Harmouch
    Genius 5255 points

    Hi Mahmoud-san,

    Thank you for your reply.

    I understood that the current sense accuracy is not depend on offset and drift is very small.

    However, the current sense current ratio K is on the data sheet.

    There is stated ± 5% accuracy when Iload is 100 mA.

    We want to correct this absolute value error.

    Is there a way to monitor the error without supply constant current etc from the outside?

    If there is any ideas, please let me know.

    Best regards,

    Tomoaki Yoshida 

  • 0 in reply to Tomoaki Yoshida91
    TI__Mastermind 28200 points

    Yoshida-san,

    The CS pin is an output and sourcing current proportional to load current. The only way to monitor the error is to measure externally he load current and the CS pin sourcing current. The ratio between the 2 measured current is the actual ratio. I do not see another way for measuring this error.

  • 0 in reply to Mahmoud Harmouch
    Genius 5255 points

    Hi Mahmoud-san,

    Thank you for your support.

    I understand that there is no way to measure the current sense error besides measuring from the outside.
    We can cancel the temperature drift if it is defined how much the slope is positive or negative, and how much will be the maximum and minimum.
    Best regards,
    Tomoaki Yoshida
  • 0 in reply to Tomoaki Yoshida91
    TI__Mastermind 28200 points

    Hello Yoshida-san, the plots verse temperature are is datasheet page 13 and 14.

    Regards, Mahmoud

  • 0 in reply to Mahmoud Harmouch
    Genius 5255 points

    Hi Mahmoud-san,

    Thank you for your support.

    I saw figure 22 - 28 in datasheet.

    But it is mean value of the three lots samples, I do not know how much the caribration effect will be at the worst condition.

    If the variation in temperature drift is large between samples, the temperature coefficient for caribration can not be decided with a fixed value.

    I think it is difficult to define min and max of temperature drift, but if it is defined it will be helpful for us.
    Best regards,
    Tomoaki Yoshida