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TPS24750: IMON inquiry

K.Shidara
Expert 3225 points
Part Number: TPS24750

Hi Team,

Would you advise below three questions about IMON?

(Question)
1. Are you assuming an application in which an AD converter is externally connected to the IMON pin of the TPS24750 to detect the current value of the SENSE resistor? If possible, could you provide an application example?

2. I could not find the relational expression to derive the current value flowing in the SENSE resistor from the IMON terminal voltage value from the datasheet and other technical data. If you have any of the above application examples, would you kindly let me know?

3. Also, if I have an AD converter connected to the IMON pin and monitor the current value, please let me know if there are any points to be aware of.

Thanks

Best regards,

Shidara

  • 0
    TI__Guru 57737 points

    Hi Shidara,

    You can easily understand the current limit and monitor circuit operation of TPS24750 with the help of the circuit highlighted below,

    From the above highlighted circuit you can deduce below two equations,

    1. Iimon = Iset

    2. Iset x Rset = Iload x Rsense (Applying KVL in the loop)

    From the above you can derive,

    Iimon = Iset = (Iload x Rsense) / Rset                                                                

    Voltage on the IMON pin, Vimon = Iimon x Rimon

    Therefore for a fixed value of Rsense and Rset you can see the voltage on the IMON pin is proportional to the load current , Iload.

    One more important point to note here is that when the efuse is in current limit mode, the voltage across IMON is regulated at 675 mV. This is how the following equation is derived.

    Unfortunately, we do not have a reference circuit for the ADC but you can consider the below points before selecting an ADC,

    • Voltage range of IMON pin 
    • Minimum current that needs to be measured. 
    • ADC full scale range. This is important to understand if you will require a gain stage in between.

  • 0 in reply to Praveen GD
    TI__Expert 3225 points

    Hi Praveen-san

    Thank you very much for the explanation.

    Please close this thread.

    Thanks

    Best regards,

    Shidara