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ADS54J66: ADS54J66- SNR & SFDR Performance

Vigneshwar Raj
Prodigy 245 points
Part Number: ADS54J66
Other Parts Discussed in Thread: LMK04828

Hello Every One,

I am planning to use ADS54J66 ADC for the input Frequency of 650MHz to 700MHz range.

I have not seen SNR and SFDR performance in Datasheet for that frequency.

I referred the performance attached in the below Link.

https://e2e.ti.com/support/data-converters-group/data-converters/f/data-converters-forum/813429/dac38j84-dac-38j84-ads54j66/3047437#3047437

But these plots are taken with -4dBFS Fundamental Power.

It will be very helpful if you are providing the following results.

1)The tested plots with -1dBFs Fundamental power in few frequency spots from (650MHz to 700MHz) 

2) The Phase Noise data of the Sampling Clock provided to ADC.

3) Input Power at which -1dBFs is reached as per the ADC front end design in Evaluation Board.

Thanks in advance,

Vigneshwar Raj

  • 0
    TI__Guru* 91947 points

    Vigneshwar,

    What sample rate for the ADC and what mode?

    Regards,

    Jim

  • 0 in reply to jim s
    TI__Guru* 91947 points

    Vigneshwar,

    Data attached. See the LMK04828 data sheet for the clock phase noise info as this was the clock source used for this test.

    Regards,

    Jim

    6840.ADS54J66_491p52Msps_bypass.pptx

  • 0 in reply to jim s
    Prodigy 245 points

    Hello Jim,

    Thanks for the immediate response.

    I check the SNR and SFDR Characteristics. I have following questions.

    1. Did you used any filter to the input signal for this measurements? If used please provide its Bandwidth details.

    2. As per the test results, SFDR is degraded due to harmonics HD3 & HD2.Are that harmonics  due to input are due to ADC internal circuit?

    3. As per datasheet @470MHz SFDR is 73 dBC. But @ 675 MHz SFDR is reduced to 55dBC.

    Hence as per test results,when increasing input frequency, it degraded ADC harmonic performance & also SFDR.

    Can you clarify why the following specification is given in datasheet.

    "Input Bandwidth (3 dB): 900 MHz" 

    4. Please share the FFT plots for 470MHz and 600MHz input frequency also.

    Thanks in advance,

    Vigneshwar

  • 0 in reply to Vigneshwar Raj
    TI__Guru* 91947 points

    Vigneshwar,

    1. I used a tunable bandpass filter from Trilithic, part number 3VF375/750-5-50-AA. I think this is a 5% filter but not 100% sure.

    2. Harmonics are mainly due to the input source. I am measuring HD2 of -43dBm and -61dBm from the source after going through the BPF.

    3.  Input bandwidth basically only measures the input amplitude response vs frequency ie how much attenuation to expect of the input signal caused by the internal sampling network. In this case, the 3dB roll off point occurs with an IF at 900MHz.

    4. Plots are attached.

    Regards,

    Jim

    2553.ADS54J66_491p52Msps_bypass.pptx