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About operation of DRV8801.

Satoshi
Guru 19495 points
Other Parts Discussed in Thread: DRV8801, DRV8800

Can DRV8801 drive following spec?  

----------------------

・Constant-current control 　

　(it is not indispensable)

・Inductance：0.22mH

・VM：24V

・Output current：1.5A

・PWM speed：20kHz

・Fall time:Less than 30us

　(at -1.5A ⇒ 1.5A)

・Can DRV8801 used with the following connection?

VPROPI output ⇒ comparator（external） input ⇒ comparator output ⇒ Enable pin input

----------------------

 

Best regards,

Satoshi

 

  • 0
    TI__Expert 8885 points

    Satoshi,

    Motor voltage,current, PWM speed and fall time specs are perfectly fine with DRV8801.

    On your first question ( constant current control ) and last (use ot VPROPI output):  

    Before answering, I would like to get clear understanding:

    My undserstanding is that VPROPI output will be compared with external referece voltage, Vref. This external reference voltage Vref, will be determined  to  represent 1.5Amp peak  motor current. Comprator logic is set in such a way that as soon as VPROPI reaches Vref, comparator will give low signal which will make Enable signal low. Is this right understanding?

    If above is right, How are you going to initiate next PWM cycle once VPROPI comes below Vref?

    Best Regards

    Milan-Motor Application Team

     

  • 0 in reply to Milan Rajne
    Guru 19495 points

    Dear Milan Rajhe-san

    Thank you for reply.

    Your thinking is right.

    The customer is designing the attached application note to reference.

    7752.slva322.pdf

    The comparator is detect VPROPI of Fig.5, and ON/OFF output.

    However, there was change to a customer's design proposal.

    Can DRV8800 detect and same control using SENSE output?

    ※SENSE output ⇒ comparator or shunt monitor（external） input & output ⇒ Enable pin input

    The customer is anxious about a noise being large.

    If there is a comparator (or shunt monitor) of reference design and recommendation, please let me know.

    Best regards,

    Satoshi

     

  • 0 in reply to Satoshi
    TI__Expert 8885 points

    Dear Satoshi-san,

    Customer apprehension about noise with DRV8800 solution is right. It would be quite risky approach to use sense output directly, with Comparator. Its max value is limited to 500mV so during small load conditions, this signal may be below 100/50mV and would be prone to external noise injection.

    I would recommend adding, external; differential amplifier (using appropriate slew-rate Opamp) stage after shunt to amplify the signal with DRV8800 approach, which in-fact would be similar to go with DRV8801.

    I don’t think that we have any reference design or application note, demonstrating use of comparator for current control.

    Best Regards

    Milan-Motor Control Application