• State TI Thinks Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 1 answer
  • Subscribers 46 subscribers
  • Views 264 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

voltage to PWM - non isolated

Alen Barisic
Intellectual 1300 points
Other Parts Discussed in Thread: ADS1208, TMS320F28379D, AMC3330

Hello,

Im looking for something to convert Voltage value to PWM similar to AMC1304M05-Q1  but NOT isolated.

I need to convert signal from Hall to PWM – can You recommend something?

Thanks,

Alen

  • 0
    TI__Mastermind 31655 points

    Hi Alen,

    You can search for the non-isolated Delta-Sigma modulators by checking the precision ADC products and filtering for a serial output: https://www.ti.com/data-converters/adc-circuit/precision-adcs/products.html#p1918=Serial

    One option that looks like it may be perfect for a Hall sensor input is the ADS1208, which has an integrated current source for driving a Hall sensor. If you have more detail on the application and sensor, I can help with part selection.

    One more thing to note is that the output of these modulator devices is not exactly a PWM. It is a bitstream of data that is output at the sampling rate of the modulator (typically 10Mhz) where the density of the 1s is relative to the input of the modulator. A PWM would have a fixed frequency with a variable duty cycle, while the modulator bitstream always outputs the same width of data on each clock edge, but it could be either a 1 or a 0. Converting this to a digital value requires additional filtering of the bitstream.


    Regards,

  • 0 in reply to Scott Cummins
    TI__Intellectual 1300 points

    Hi Scott,

    thank you for the information.

    after review of the project I need to improve one thing and I want to add isolated ADC to compare performance to HALL Sensor if it makes sense:

    1. Converting Voltage Single Ended signal from Allegro Hall Sensor in range 0-5V ( I have doubts it it will be robust )
    1. Option 1 is to convert it to PWM –  not sure your solution is not to complicated – lets try option 2.
    2. Option 2 is to convert it to Current Signal – do You have Regulated Current source which I can use with proper dynamic to restore Current Signal 150kHz ?
    3. Option 3 – if there won’t be other option I will use differential output from OPAM
    • Do You think that any of isolated ADC can be used to measure 150kHz Current? There are in theory clock in range 10MHz but later there is info that after implementation of filtering bandwidth is only in range of 70-80kHz. I want to put on board in addition such isolated ADC to compare performance.

    Regards,

    Alen

  • 0 in reply to Alen Barisic
    TI__Mastermind 31655 points

    Hello Alen,

    Where will the digital data be handled? Are you using an FPGA or a microcontroller? The modulator's bitstream output is usually fed into a Sigma Delta Filter Module (SDFM) that is integrated into a microcontroller, or built inside an FPGA. An example of an MCU that includes a SDFM is one of the C2000s such as the TMS320F28379D. If your system already includes a controller with the capability to handle this bitstream then you're already done. If not, there may be some better options available. 

    Another option would be to use an isolated amplifier instead. These have an analog output that you would then need to convert to PWM, or use another component to convert it to a current output. Either way will require some extra circuitry on the low side, but with an amplifier like the AMC3330, you would only need to power the lowside, so you save components for power on the high side. 

    Can you give a little more detail on the required inputs and outputs of your system? Since you mention you are using a Hall sensor I imagine you're measuring a voltage, but you also ask about measuring a 150khz current source. Whether you're measuring a voltage directly or current through a shunt will determine which device is recommended, since they have input ranges optimized for each application.


    Regards,

  • 0 in reply to Scott Cummins
    TI__Intellectual 1300 points

    Hi Scott,

    thank you for the explanations and sorry for the confusion.

    the application is to measure a current with a hall sensor which has a voltage output. That is why we are thinking of converting this voltage output to current or PWM to be more robust.

    The voltage to current conversion is the preferred way to go. Do we have an existing solution for such conversion? A Regulated current source with proper dynamic to restore Current Signal 150kH or the differential output of an op amp? Could you maybe bring this thread to the attention to someone of the corresponding teams?

    Do You think that any of isolated ADC can be used to measure 150kHz Current? There are in theory clock in range 10MHz but later there is info that after implementation of filtering bandwidth is only in range of 70-80kHz.

    thank you for your efforts.

    Regards,

    Alen