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Original question:

Can ADS1293 work with Ceramic Resonators?

ADS1293: Connection to Resonator

Carlo
Expert 7715 points
Part Number: ADS1293


Hi team,

Good day.

Our customer  would like to know the connection between the ADS1293CISQ with the resonator from Murata which is CSTNR4M00GH5L000R0. The datasheet indicates that pin23 XTAL 1 and pin24 XTAL2 are both digital input pins and taking a look in Figure 84, these pins are connected to VDD. However, the EVM shows that the external crystal is connected to VDD and AGND. Please confirm what is the appropriate connection for the resonator?

Thank you in advance for your help.

Regards,
Carlo

  • 0
    TI__Guru 66716 points

    Hello Carlo,

    Thank you for posting your customer's question.

    The oscillator is a digital signal and should have been referenced to the digital supplies: VDDIO and VSSIO. Nice catch!

    Fortunately, on the ADS1293EVM, VDD and VDDIO both operate at 3.3-V levels. From the EVM schematic, you can see that all supplies are generated using the LP2985AIM5-3.3 LDO. This explains why the EVM still functions as-is, but external analog and digital supplies could cause a problem.

    Thanks for bringing this to our attention.

    Best regards,

  • 0 in reply to Ryan Andrews
    TI__Expert 7715 points

    Hi Ryan,

    Good day.


    Thank you for the clarification about this. However, how can we connect the CSTNR4M00GH5L000R0 resonator to ADS1293CISQ? The resonator has 3 terminal pins 1 Input, 2 GND, 3 Output, thus it mean that it's not compatible?

    Regards,
    Carlo

  • 0 in reply to Carlo
    TI__Guru 66716 points

    Hi Carlo,

    A crystal resonator is not the correct device to use for the clock input. The crystal below is the component used on the ADS1293EVM:

    https://www.digikey.com/product-detail/en/ecs-inc/ECS-41-18-5PXEN-TR/XC1680TR-ND/2213782

    Best regards,

  • 0 in reply to Ryan Andrews
    TI__Expert 7715 points

    Hi Ryan,

    According to our customer, they've been using the resonator with  ADS1293 for years with no issues. They would like to ensure that the connections of the resonator to the device are appropriate and looking for some documentation or technical data indicating the use of a resonator with ADS1293. As I checked the relevant documentation for this device, a crystal was also used on reference designs. Can you confirm if we have any application notes that used a resonator instead of crystal for ADS1293?

    Thank you.

    Regards,
    Carlo

  • 0 in reply to Carlo
    TI__Guru 66716 points

    Hi Carlo,

    I understand. In that case, I would like to review the customer's schematic and see how this is connected in their system. You can post just a partial schematic containing the ADS1293 and the resonator. Typically, a single-ended clock, such as the output of a crystal oscillator, would be applied to the CLK pin with a nominal frequency of 409.6 kHz. 

    I don't recall seeing a resonator used in the past, but I'd be happy to review the reference designs you are referring to as well.

    Best regards,

  • 0 in reply to Ryan Andrews
    TI__Expert 7715 points

    Hi Ryan,

    Here is the ads1293 resonator connection.

    Thank you.

    Regards,
    Carlo

  • 0 in reply to Carlo
    TI__Guru 66716 points

    Hi Carlo,

    Thanks for sharing a portion of their schematic.

    After review the measurement diagram in the resonator datasheet, I believe it is connected correctly in the customer's schematic above. The orientation of pin 1 vs. 3 relative to the ADS1293 should not make a difference. Pin 2 should be referenced to the digital ground of the circuit.

    Best regards,