• State TI Thinks Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 2 answers
  • Subscribers 29 subscribers
  • Views 518 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

DRV8825: ISENSEx current

Dukel
Intellectual 610 points
Part Number: DRV8825
Other Parts Discussed in Thread: DRV8886, DRV8886AT,

Hi,

What would be the max. current coming from the ISENSEx pins? The datasheet states that it can transient up to ±1[V] but not the max. current. I want to use a 0.1[ohm] resistor but not sure what package to use.

Best regards,

Dukel

  • 0
    TI__Guru** 114905 points

    Hi Dukel,

    The max current is the Ifs current set by VREF and the sense resistor.

    Assuming the Ifs = 2.5A, the max current can vary by +/-5%.

  • 0 in reply to Rick Duncan
    Intellectual 610 points

    Hi Rick,

    Yes that's the current which the motor driver can supply, but is it the current on the ISENSEx pins as well? This would mean that the the Watt on the RISENx would be 0.8*2.5= 2[W]. That is a lot of energy just for one resistor.

  • 0 in reply to Dukel
    TI__Guru** 114905 points

    Hi Dukel,

    Yes it is the current on the ISENSEx pins also.

    And yes the power on the resistor could be as high as 2W.

    That is why the sense resistor is typically 0.1 to 0.2 Ohms, which lowers the power.

    If you need less than 2A and would like to eliminate the sense resistors (and the power), the DRV8886 or DRV8886AT are alternatives.

  • 0 in reply to Rick Duncan
    Intellectual 610 points

    Hi Rick,


    Thank you for you reply and answer. The DRV8825 is perfect for me and I'm already using it, but in my new design I was wondering if could change the package size of the RISENx. Currently using 1206 but in the rest of my design I'm using 0603.

    1206 resistors should be able to withstand 1/8[W] which is not even close to the 2[W] that could be if I understand you answer right. So my eventual question is. Can I use a 0603 size resistor of 0.1[ohm] this can endure even less power but the 1206 shouldn't be able to withstand it as well.

    The datasheet doesn't recommend a package size.

    Best regards,

  • 0 in reply to Dukel
    TI__Guru** 114905 points

    Hi Dukel,

    We don't recommend a package size because we do not know the application. The device can be used for up to 2.5A, but can be used for much less. Also the resistor value can be increased for better accuracy or decreased for better thermals.

    All the current through the motor goes through the resistors, except when slow decay is in operation.

    The worst case current through the resistor is when the motor is stopped at 100% of Ifs in the indexer table (in microstep mode) or 71% of Ifs in full step mode.

    Ifs is set by the application.

    On the EVM with a max Ifs of 2.5A, a .2 Ohm, 2512, 2W SMD resistor is used. This max power through this resistor is 1.25W

    If your current is less, you can use lower wattage resistors or place a few resistors in parallel.