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.

  • Resolved

ADS1263: Application consultation:

Expert 2065 points

Replies: 1

Views: 73

Part Number: ADS1263

hi,

At present, ADS1263 is selected. Some questions need to be consulted:

 1. Does the chip have to support differential?

        2. What is the role of the third pin AINCOM, how to use it?

        3. Is there a crystal oscillator of the 15th and 16th crystal oscillator pins that can only be connected to the MCU? If it can be connected to an external crystal oscillator, what's the difference between using crystal oscillator of MCU?

Our demand is: the analog acquisition voltage value is our power supply voltage, which is initially determined to be 5V, 3.3V, 1.3V, multi-channel acquisition, 32-bit high precision, because MCU resources are limited, so try to occupy as little as possible The resources of the MCU.

Can the chip meet the requirements?

thanks.

  • Hi Wu,

    I'd be glad to help answer your questions regarding the ADS1263...

    1. The ADS1263 always measures voltages differentially between two input pins.
      However, this doesn't necessarily mean that you could not measure a single-ended input (for example, which you can think of as being differential, but referenced to ground potential instead of having a second signal wire).  But, you do need to take care to ensure that the input signal, whether single-ended, differential, or pseudo-differential, does not violate the internal PGA's common-mode range. To assist with this determination, I would recommend downloading the ADS126X-CALC-TOOL which has a PGA common-mode calculator.

    2. AINCOM is just another analog input pin which can be selected by the internal MUX. However, it does provide an internal 2.5V bias voltage (meaning it will output 2.5V) so that you can connect a floating sensor (like a thermocouple) OR measure a single-ended signal with respect to 2.5V , since you generally cannot ground any of the analog inputs without violating the PGA's common-mode range (not unless AVSS is a negative voltage).
    3. The ADS1263 allows for 3 different clock sources...

      1. The internal oscillator
      2. An external crystal
      3. An external clock source, such as an MCU clock

        There is no difference really between using an external clock from a dedicated crystal oscillator circuit or from an MCU clock; however, generally when using an external clock source the main concern is reducing the clock jitter on the ADC's master clock. Most likely the crystal oscillator would provide a cleaner clock than an MCU. However, if you need the ability to adjust the ADS1263 data rates (more so that you can via the device's DR[3:0] register field), then you may prefer the flexibility to programmatically adjust the ADC's clock frequency from the MCU clock.

         

    Regarding your comment about the ADS1263's ability to measure different power supply voltages...
     
    I think you can measure all of these supplies, but you'll probably have to BYPASS the PGA. You definitely cannot ground any of the analog inputs while the PGA is enabled, and connecting any input pin to 5V while the PGA is enabled will also be a problem.

    Another thing to consider is will the ADS1263 ever be OFF while connected to these supply voltages? If so, you'll need to limit the input current (with a series resistor) to make sure the input current never exceeds 10 mA, otherwise you may damage the device.

    The combination of bypassing the PGA and adding a series resistance is not ideal, but if you keep the series resistance low (between 500 Ohms and 2k), you'll probably get okay performance. Also keep in mind that the supply noise will be observable in the ADC's conversion result, so unless you have a very clean supply you may not benefit much from the ADS1263's 32-bit resolution; you might be fine with a 24- or 16-bit ADC.

    Best regards,
    Chris Hall
    Applications Engineer | Precision ADCs


    Check out these helpful resources...
    TI Precision Data Converters | TI Precision Labs - ADCs | Analog Engineer's Calculator | Data Converters Learning Center | Selection Guide

     

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.