• State Resolved
  • Locked Locked
  • Replies 14 replies
  • Subscribers 31 subscribers
  • Views 1513 views
  • Users 0 members are here
Support feedback
Options
Options
Related

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.

DRV8306: Current limit function

Hirotaka Matsumoto
Guru 27595 points

Part Number: DRV8306

Hi all

Would you mind if we ask DRV8306?
Please refer to the attachment file.
20190425_DRV8306.pdf

Our customer's setting of ILIM=15A, however it seems that current is clamped with 6A.

<Question1>
The current limit function is relation to Rsense only, isn't it?
If it has other current limit, could you let us know?

<Question2>
We assume that ILIM formula is as follow;
-ILIM=Vlimit/Rsense
Is it correct?

Kind regards,

Hirotaka Matsumoto

  • 0
    TI__Guru 66550 points
    Matsumoto-San,

    There is SEN_OCP and VDS_OCP, both have their own settings, has the customer checked the limits of both?

    Regards,

    -Adam
  • 0 in reply to Adam Sidelsky
    Guru 27595 points

    Adam san

    Thank you for your reply.

    The customer's waveform shows limitation of current with 6A.
    So, we assume that it is cause of ILIMIT function.
    Are the setting of SEN_OCP and VDS_OCP relation to ILIMIT?
    We assume that SEN_OCP and VDS_OCP are relation to OCP.

    Kind regards,

    Hirotaka Matsumoto

  • 0 in reply to Adam Sidelsky
    Guru 27595 points

    Adam san

    We add the information.
    20190426_DRV8306.pdf
    It seems that ISEN-GND is less than VLIMIT(0.25V), however the current is clamped.

    And then, the customer confirmed with VDS=75kohm, however the result was the same. 

    Kind regards,

    Hirotaka Matsumoto

  • 0 in reply to Adam Sidelsky
    Guru 27595 points

    Adam san

    We guess that your days are so busy, however could you let us know your circumstance?

    Kind regards,

    Hirotaka Matsumoto

  • 0 in reply to Hirotaka Matsumoto
    TI__Guru 66550 points
    Matsumoto-San,

    Yes my days are very busy.

    VDS_OCP is configurable from 0.15V up to 1.8V. The customer can select the VDS resistor to control this. What is their VDS pin configuration?

    SEN_OCP is fixed at 1.8V, this feature is related to ILIMIT because the sense resistor is used for both SEN_OCP and VLIMIT.

    Can the customer try different VDS_OCP setting and check if the issue is resolved?
    Can the customer try lower RSENSE and see if the issue is resolved?

    Regards,

    -Adam
  • 0 in reply to Adam Sidelsky
    Guru 27595 points

    Adam san

    Thank you so much for your reply.

    What is their VDS pin configuration?
    ->We heard that they configured VDS 75 kΩ (±5%) to AGND. We will confirm it again.

    Can the customer try different VDS_OCP setting and check if the issue is resolved?
    ->We will feedback you later.

    Can the customer try lower RSENSE and see if the issue is resolved?
    ->We will feedback you later.

    Kind regards,

    Hirotaka Matsumoto

  • 0 in reply to Adam Sidelsky
    Guru 27595 points

    Adam san

    We add some information.

    What is their VDS pin configuration?
    ->We heard that they configured VDS 18kΩ (±5%) to DVDD. VDS_OCP might be 1.8V.

    Can the customer try different VDS_OCP setting and check if the issue is resolved?
    ->Even though VDS_OCP might be 1.8V, the issue is not resolved.

    Can the customer try lower RSENSE and see if the issue is resolved?
    ->We will feedback you later.

    Kind regards,

    Hirotaka Matsumoto

  • 0 in reply to Adam Sidelsky
    Guru 27595 points

    Adam san


    Can the customer try different VDS_OCP setting and check if the issue is resolved?
    Can the customer try lower RSENSE and see if the issue is resolved?
    ->Please refer to the attachment file.
    20190507_DRV8306.pdf

    And then, we changed VDS threshold with all patern, however the issue is not resolved.
    So, it seems that it is not relation to VDS threshold and ILIMIT setting.
    If you have any idea, couldy you let us know?
    We are sorry to hurry you, however the customer has to resolve this problem urgently.

    Kind regards,

    Hirotaka Matsumoto

  • 0 in reply to Adam Sidelsky
    Guru 27595 points

    Adam san

    Thank you for your support always!

    We attach additional information.
    20190508_DRV8306.pdf

    This waveform shows VM current, U motor current and V motor current.
    And then, we would like to send you customer's circuit.
    It contains confidential contents, we would like to send you it by private message on E2E.
    Could you accept "friend request"?

    Kind regards,

    Hirotaka Matsumoto

  • 0 in reply to Adam Sidelsky
    Guru 27595 points

    Adam san

    We assume that your days are so very busy.
    However, if you have some advice, could you let us know?

    Kind regards,

    Hirotaka Matsumoto

  • 0 in reply to Hirotaka Matsumoto
    TI__Guru 66550 points
    Hirotaka-San,

    Which model of motor is this? What is the VM applied? What RPM is the customer spinning when the current clamp is occuring?

    Regards,

    -Adam
  • 0 in reply to Adam Sidelsky
    Guru 27595 points

    Adam san

    Thank you so much for your support!

    Which model of motor is this?
    What RPM is the customer spinning when the current clamp is occuring?
    ->We will feedback you later.

    What is the VM applied?
    ->33V.

    When the customer changed FET whose RON is lower, it seems that the clamp failure is resolved.
    VDS setting is configured VDS 18kΩ (±5%) to DVDD.
    VDS_OCP might be 1.8V.
    It is big VDS_OCP, so it seems that VDS is not more than VDS_OCP.
    We think that we should measure VDS pin voltage.
    In case of VDS 18 kΩ (±5%) to DVDD, how much is VDS-pin voltage?

    Kind regards,

    Hirotaka Matsumoto

  • 0 in reply to Hirotaka Matsumoto
    TI__Guru 66550 points
    Matsumoto-San,

    Per the datasheet section: SEVEN-LEVEL INPUTS (IDRIVE, VDS)

    With 18k to DVDD, the VDS pin should see 2.8V. Yes I would recommend checking the VDS pin voltage to confirm that the pin is seeing 2.8V and therefore the VDS sensing is configured as 1.8V as intended.

    Regards,

    -Adam
  • 0 in reply to Adam Sidelsky
    Guru 27595 points

    Adam san

    Thank you for your DRV8306's support always!

    As the conclusion, it seems that the customer board has some wrong point about layout.
    There is the pattern resistance 40mohm between RISENSE and GND.
    Now, they check their board's layout.

    Therefore, the device is normal operation.
    We really apologize any problems that they have caused.

    Kind regards,

    Hirotaka Matsumoto