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AFE5808A: Inquiry

Ray Vincent Aranzaso
Genius 15475 points
Part Number: AFE5808A
Other Parts Discussed in Thread: AFE5808

Hi,

Good Day.

1. If I use internal reference mode, should I bypass the VREF pin (M3) with 0.1 uF? (we know this set-up is for external reference mode)

2. Clock input amplitude VCLKP_ADC (single-ended, LVCMOS) must be 1.8V? Why is 3.3V (ECS-3953M-400-BN) used on AFE5808_08AEVM?

Please advise. Thank you very much.

Best Regards,

Ray Vincent

  • 0
    TI__Expert 6790 points

    Hi Ray,

    Thanks for reaching out.

    Please find the response to your questions inline.

    1. If I use internal reference mode, should I bypass the VREF pin (M3) with 0.1 uF? (we know this set-up is for external reference mode)

    TI: Yes, in internal reference mode, you can bypass the pin to gnd with 0.1 uF capacitor.

    2. Clock input amplitude VCLKP_ADC (single-ended, LVCMOS) must be 1.8V? Why is 3.3V (ECS-3953M-400-BN) used on AFE5808_08AEVM?

    TI: Good observation Ray, I think they should have used 1.8V oscillator instead of 3.3V one. Since these boards were developed long ago, I'm not sure why they used the same. May be for simplicity and part availability.

    However, this will not affect the device in any way because there will be a protection ESD diodes that will take the overload and pass the current. Also, there is a 50 ohm series resistor that will limit the current. Hence, the device will still remail fully functional without any issue.

    I hope this answers your questions. 

    Thanks & regards,

    Abhishek

  • 0 in reply to Abhishek Vishwa1
    TI__Genius 15475 points

    Hi Abhishek,

    Good Day. I will ask questions in a different way. Can I leave a floating VREF pin (without 0.1 uF capacitor) in internal reference mode?
    In some ICs, the voltage reference pin is bidirectional and the bypass capacitor it is recommended to use even in internal reference mode.

    Please advise. Thank you very much.

    Best Regards,

    Ray Vincent

  • 0 in reply to Ray Vincent Aranzaso
    TI__Expert 6790 points

    Hi Ray, 

    The bypass capacitor is required on the VREF pin in both internal and external reference mode.

    Thanks & regards,

    Abhishek