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DRV8302: How to connect DRV8302 overcurrent protection circuit

Annie Liu
Genius 10295 points
Part Number: DRV8302

Hi Team,

The customer refers to the overcurrent protection circuit connected to the DRV8302 Datasheet, but obviously feels wrong. 

Adopt 1: 1 partial pressure (we use MOS tube R (on) = 3.6mΩ) current limit to 450A. In actual applications, such a large current is not reached, but an overcurrent error will still be reported. Is the customer understanding wrong? Can the overcurrent protection function be achieved by directly dividing the two resistors in practical applications?

Best Regards,

Annie

  • 0
    TI__Guru 65320 points

    Annie,

    Please show us a diagram or schematic of the board you are using and let us know any settings that you have made.

    Regards,

    -Adam

  • 0 in reply to Adam Sidelsky
    TI__Genius 10295 points

    Hi Adam,

    I apologize for any delay in responding to your email. Customer provided the schematic just now.

  • 0 in reply to Adam Sidelsky
    TI__Genius 10295 points

    Hi Adam,

    Customer also attached MOS tube circuit.

  • 0 in reply to Annie Liu
    TI__Guru 65320 points

    Annie,

    Some comments on the schematic:

    1. SS_TR capacitor is missing.
    2. M_PWM has a resistor pull up and short to GND, is R82 populated?
    3. DC_CAL must be low for the sense amplifiers to operate, can you confirm this?
    4. BST caps are higher than the EVM.
    5. CSA input paths have 100 ohms on both the SN and SP lines, we do not recommend this, there should be no series resistance here.
    6. What is the purpose of R12?

    Likely the resistance in the CSA path is causing your issue.

    Regards,

    -Adam

  • 0 in reply to Adam Sidelsky
    TI__Genius 10295 points

    Hi Adam,

    The following operations have been done by customer when trying the experiment current limit logic (R17 = 10k; R21 = 330R; calculated current limit 30A):

    1. Connect a power load (0.1R) between the AB two-phase outputs, collect current through an oscilloscope, control the A + B- conduction to grab the waveform, and display the current rises to about 26A to trigger protection, which is close to the theoretical value;

    2. The lower tubes (A-, B-, C-) are fully closed, there is no load between each phase, and only one upper tube (A +) PWM is turned on, then the protection is triggered after 2 to 3 PWM cycles;

    3. When the BLDC inductive load is actually connected, if the duty cycle adjustment increases too fast, nFault is also easily triggered;

  • 0 in reply to Annie Liu
    TI__Guru 65320 points

    Annie,

    These behaviors are expected, please let us know if you have any other questions.

    Regards,

    -Adam