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Original question:

DRV8832- Isense voltage measurement

DRV8832: Sensing 100mA stall current

Nelson Ho
Prodigy 20 points
Part Number: DRV8832

Hi,

The data sheet mentioned that the minimum Rsense is 1ohm, meaning that the lowest reportable motor stall current is 200mA. I would like to sense stall condition at 100mA. Here are my questions
1) What would happen is Rsense is 2ohm
2) How would you recommend detecting this condition - would external AD converted to detect the voltage across Rsense at 01V be the only way possible to check for the condition?
3) Is there any other TI part that is suitable for doing this?

Thank you.

  • 0
    TI__Guru** 114905 points
    Hi Nelson,

    Please refer to the thread: e2e.ti.com/.../748665 for more information.

    Using a 2 Ohm resistor should work, but you should consider the variation of the Itrip voltage.

    The datasheet has not yet been updated.
  • 0 in reply to Rick Duncan
    Prodigy 20 points
    Thank you Rick,

    If I understand the data sheet correct, the voltage across the current sensing resistor would be 200mV and then fault condition would be triggered if condition persists for 275mSec.

    I did a search on the data sheet and it seems that Itrip is an internal comparator output. Can you clarify what do you mean by consider the variation of the Itrip Voltage? Do you mean I have to make sure the startup current is taken into consideration and that also would not exceed 100mA for 275 mSec?

    Or do you mean I have to be careful in selecting the resistor capable of handling the power going through the 2 Ohm resistor.

    Thank you!
  • 0 in reply to Nelson Ho
    TI__Guru** 114905 points
    Hi Nelson,

    Sorry. I was not clear. I should have said VIlim instead of Itrip voltage. Vilim is typically 200mV, but can vary +/-20%.

    Because of this variation, some devices could begin regulating the current at 80mA (160mV/2Ohms) while others at 120mA (240mV/2Ohms).

    The fault condition is triggered if the device reaches the current regulation point in every PWM cycle for 275ms. If one PWM does not reach the current regulation point, the count is reset to 0 and begins again.