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DRV8841: DRV8841 about design issues

Mickey Zhang
Genius 12080 points
Part Number: DRV8841

Hi team,

The customer is using DRV8841. 

In first mode it should pump around 200mA where as in another mode it should drive around 80mA current.

The attached is the customer's schematics based on DRV8841IC for drive circuit where SOV load is around 60 Ohm, 6.5mH.

The customer evaluates this circuit in breadboard. Followings are the customer's ideas:

1. When load is not connected & the customer  is enabling the driver A or B, the AOUT/BOUT is a PWM signal with 4uS as turn off time & time period of 20uS.

2. When SOV load is connected with a condition of 100% bridge current, the AOUT/BOUT is showing continuous 28V in place of an expected PWM signal of different duty cycle.

Q1: Is there any problem for the customer's ideas?

Q2: Is the customer's schematics correct?

Q3: Can you give me some suggestions for the customer's design?

Best Wishes,
Mickey Zhang
Asia Customer Support Center
Texas Instruments

  • 0
    TI__Guru** 114905 points
    Hi Mickey,

    We will investigate and reply soon.
  • 0 in reply to Rick Duncan
    TI__Genius 12080 points

    Hi Rick,

    Sorry. Please check the attachment.

    Modified_Design.pdf

  • 0 in reply to Mickey Zhang
    TI__Guru** 114905 points
    Hi Mickey,

    1. When load is not connected & the customer is enabling the driver A or B, the AOUT/BOUT is a PWM signal with 4uS as turn off time & time period of 20uS.

    2. When SOV load is connected with a condition of 100% bridge current, the AOUT/BOUT is showing continuous 28V in place of an expected PWM signal of different duty cycle.


    I would expect the opposite:

    In condition 1, I would expect continuous 28V. In condition 2, I would expect a PWM signal at the output.

    Can you confirm the output connections are correct?

    Also, I will discuss the configuration with the design team. This is unusual.
  • 0 in reply to Rick Duncan
    TI__Genius 12080 points
    Hi Rick,

    Thank you for your reply.
    Q1: Is the customer's schematics correct?
    Q2: What do you mean by confirm the output connections are correct?
  • 0 in reply to Mickey Zhang
    TI__Guru** 114905 points
    Hi Mickey,

    Q1: Is the customer's schematics correct?

    The circuit looks like it should work. As mentioned, it is not a standard connection. I want the design team to examine the schematic to confirm it will work.

    Q2: What do you mean by confirm the output connections are correct?

    Please confirm that :
    The load is not connected when the AOUT/BOUT is a PWM signal with 4uS as turn off time & time period of 20uS.
    The load is connected when the AOUT/BOUT is showing continuous 28V

    Would you also ask for a scope capture of the current, AOUT1, and AOUT2 for both conditions?