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Original question:

ADS131A04: ADS131A04 Crystal problems

ADS131A04: Oscillator problems on this ADC

Martin Karlsson
Prodigy 90 points
Part Number: ADS131A04

Hello,

I was in contact with TI ~1 year ago about oscillation problems. We use a suggested crystal and have worked a lot with the load capacitors.

Now I see more customers having problems with this, has TI done some die shrinking? Since we are seeing more frequently errors and getting products back from the market that has passed all EOL test.

Please explain how the oscillator is implemented in the die and why there is a sensitivity problem.

Best regards,

Martin

  • 0
    TI__Mastermind 35600 points

    Hi Martin,

    I double checked the record on the E2E forum. I believe the following query was the post/communication around 1 year ago as you mentioned. My colleague had requested our design team did a simulation and the result showed that both XTAL pins on ADS131A04 have approximately 2pF input capacitance which are relatively low. 

    ADS131A04: ADS131A04 Crystal problems

    The ADC uses an external crystal similar to a pierce oscillator with the inverter in contained inside the device, which is shown in the figure below:

    Can you please let me know if you are still using the crystal (ABLS-16.384MHZ-L4Q-T) with two 10pF capacitors? Also, could you please post your pcb layout (top and bottom layer) for the area of crystal and the ADC? I did not receive other reports about oscillator problems on this ADC, however I would check with the engineers who supported this device before to see any possible suggestions.

    Best regards,

    Dale

  • 0 in reply to Dale Li
    TI__Mastermind 35600 points

    Hi Martin,

    I haven't heard back from you for a while, however I already had an internal discussion with our team, this is really related to the layout capacitance, capacitor capacitance and so on, it's the result of the combination of all factors. Generally, an external clock from microcontroller/FPGA or oscillator is more reliable.

    Best regards,

    Dale