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ADS4142: external capacitance on CLKOUT

NAOKI AOYAMA
Guru 11215 points

Part Number: ADS4142

Hello,

Our customer use the ADS4142, with parallel CMOS mode.

The customer connect a capacitance (less than 10pF) between CLKOUTP and GND

to reduce output noise.

When the customer remove this capacitance, there are a lot of noise on the output signal.

Is it possible to connect a capacitance? or not recommend?

Best Regards,

Naoki Aoyama

  • 0
    TI__Guru* 91947 points

    Naoki,

    What is the CLKOUT driving? How long is this trace? There is a good chance you are seeing reflections on this trace. If possible, can you place a series resistor around 22.1 Ohms as close as possible to the ADC? Another option is to add termination at the load. The EVM uses a buffer device between the ADC and the output connector. This is another option.

    Regards,

    Jim 

  • 0 in reply to jim s
    Guru 11215 points
    Hello Jim,

    Thank you for your reply.

    The CLKOUT is driving FPGA in short trace. The customer place series resistor 22 Ohm.
    Because the customer's measurement tool is very poor, so we can't analyze true signal (without capacitance).

    I will suggest the customer to adjust the value of the series resistor.

    Thanks,
    Naoki Aoyama