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CC1310: Creating a programmable voltage reference with CC1310 in standby mode

Nicholas Carley
Genius 10445 points
Part Number: CC1310
Other Parts Discussed in Thread: CC1312R

Hello,

My customer is using a CC1310 in standby mode and needs to be woken up by a comparator but they need the reference voltage of that comparator to be adjustable.

One thought I had was to use the sensor controller to set a GPIO to PWM mode then use an LC filter to create a DC voltage from it. But its unclear to me if this is possible on the sensor controller and how to understand the power consumption of a GPIO in such a mode.

Another option would be the current source into a shunt resistor to set a voltage on the output, is that a viable use case of the current source?

Nick

  • 0
    TI__Guru**** 317180 points

    - CC1312R would have been a better choice here since this part has a DAC that can generate a reference.

    - Why do they need a programmable reference? Would it be possible to scale the input signal and not the reference?

    - If opening the help for Sensor Controller Studio and select COMPA: The figure show that the ISRC source will be connected to both inputs of the comparator since this is targeting cap sense.

    - A PWM approach could potentially work but I would assume that the current consumption could be too high. What is the required accuracy? I don't know the leakage on this node and hence it's difficult to know how often the GPIO has to toggle to keep the voltage. But how do you ensure that the voltage after the filter is what you want? 

  • 0 in reply to TER
    TI__Genius 10445 points

    - CC1312R would have been a better choice here since this part has a DAC that can generate a reference.

    • This may be an option, I will discuss it with them

    - Why do they need a programmable reference? Would it be possible to scale the input signal and not the reference?

    • Depending on environmental conditions the signal (going into the comparator) will have a varied DC steady state voltage so adjusting the reference of the comparator before going into standby mode is an easy fix without needing a PGA op-amp which is more expensive

    - If opening the help for Sensor Controller Studio and select COMPA: The figure show that the ISRC source will be connected to both inputs of the comparator since this is targeting cap sense.

    • I understand this to mean the ISRC isn't available external to the device? We are planning to use an external comparator.

    - A PWM approach could potentially work but I would assume that the current consumption could be too high. What is the required accuracy? I don't know the leakage on this node and hence it's difficult to know how often the GPIO has to toggle to keep the voltage. But how do you ensure that the voltage after the filter is what you want? 

    • This is a really good point. I think that makes this option a no go without waking up the CC1310 often.

    Nick

  • 0 in reply to Nicholas Carley
    TI__Guru**** 317180 points

    I answered under the assumption that they wanted to use the internal comparator as a wake-up. Based on the figure in the Sensor Controller help it looks like you can use this externally if you are not actually using COMPA. This should be fairly easy to test out using a Launchpad. 

  • 0 in reply to TER
    TI__Genius 10445 points

    No worries, thank you for the help. I will work with the customer on potentially #1 or #3 as a solution.

    I'll mark this resolved and open up a new thread if needed.