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DRV2665: Generate programmable constant +/-DC output

Anvesh Reddy Nallamaddireddy
Prodigy 40 points
Part Number: DRV2665
Other Parts Discussed in Thread: DRV8662, , DRV2700

Hello Team,

I would like to get constant +/-DC voltage? like -20V, -5V, 0V, +60V, +70V (approx values)

Ca this be acheived with any of the following approaches?

1.)  with using I2C programming alone by loading FIFO with a constant value

2.) connect 2 PWM sources to IN+ and IN- and drive either one of them at a time

3.) connect a ADC with out put range of +/- 1.8V (in non-differential mode) to IN+

Please suggest any other appropriate approach if feasible with DRV8662 or any other IC

Thanks and Regards,

Anvesh Reddy.

Student Research assistant,

Fraunhofer ISE,

 Heidenhofstrasse 2,

79110 Freiburg im Breisgau,

Germany.

  • 0
    TI__Guru* 84915 points

    Hi, Anvesh,

    Welcome to E2E and thank you for your interest in our products!

    I think the best solution for this would be use an analog input (PWM or ADC) but removing the input capacitors from the DRV2665 input. The input capacitors work as a DC blocking filter (or high-pass filter with the combination of the input impedance). So, if you are looking for a DC level, you will need to remove this capacitor.

    If you use a PWM signal, I would suggest to use an RC low-pass filter to remove the high-frequency content and just leave the DC component. A 30KHz filter could be useful for this case.

    Please let me know if you have additional questions or comments.

    Best regards,
    Luis Fernando Rodríguez S.

  • 0 in reply to Luis Fernando Rodriguez S.
    Prodigy 40 points

    Yes, that clarified my doubt, thanks. Can you clarify on below points as well:

    Does PWM signal at IN- gives negative voltage at Out1 terminal w.r.t Out2?

    And should I be placing any pulldown resistor in addition to LPF, as I am intending to use only one of IN terminal at a time?

    Thanks and Regards,

    Anvesh Reddy.

    Student Research assistant,

    Fraunhofer ISE,

     Heidenhofstrasse 2,

    79110 Freiburg im Breisgau,

    Germany.

  • 0 in reply to Anvesh Reddy Nallamaddireddy
    TI__Guru* 84915 points

    Hi, Anvesh,

    Sorry, I think I made a mistake on my previous post. I just talked with the design team regarding this and they mentioned that the input capacitors cannot be removed. Let me clarify a little bit about how the device inputs and outputs work, so you will have a better approach for your design.

    The analog inputs work with a common-mode level which is defined by VDD. The common-mode level is actually VDD/2 and you can measure it on each input when the device is in idle state. Similarly, the outputs will have a common-mode level defined by PVDD/2 in idle mode. So, if IN+ is above VDD/2, OUT+ will be above PVDD/2. There's a direct relation on IN+ with OUT+ and IN- with OUT-

    So, if the input capacitors are removed, there could be a misbehavior on the common-mode level. And the output won't work correctly. This behavior unfortunately won't allow to have DC input level since the input capacitor will block your DC signals.

    Best regards,
    Luis Fernando Rodríguez S.

  • 0 in reply to Luis Fernando Rodriguez S.
    Prodigy 40 points

    HI Luis,

    But can I use DRV2700 as DC-Coupled DAC  as specified in it datasheet to achieve desired constant DC output voltage?  OR any other IC that you can suggest.

    Thanks and Regards,

    Anvesh Reddy.

    Student Research assistant,

    Fraunhofer ISE,

     Heidenhofstrasse 2,

    79110 Freiburg im Breisgau,

    Germany.

  • 0 in reply to Anvesh Reddy Nallamaddireddy
    TI__Guru* 84915 points

    Hi, Anvesh,

    Yes, both DC- input applications can be used but for differential mode only. Single-ended DC applications must not be tried.

    Best regards,
    Luis Fernando Rodríguez S.

  • 0 in reply to Luis Fernando Rodriguez S.
    Prodigy 40 points

    But the application circuit of DRV2700 section 9.2.3 Fig 34, explains the IC can be used to generate constant voltages.

  • 0 in reply to Anvesh Reddy Nallamaddireddy
    TI__Guru* 84915 points

    Hi, Anvesh,

    Yes, the DC coupled input can be used to generate the constant output voltage. The device should be used as specified in figure 34 or 35 (both applications are in differential mode). Single-ended mode or single input applications should be avoided.

    Best regards,
    Luis Fernando Rodríguez S.