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DAC3484: effect on image frequencies?

Furkan Fehmi Sefiloglu
Expert 3118 points
Part Number: DAC3484

Hi Team,

Can you please check and advise with following request?

"

1. As far as we understood from the DAC3484 graphics, it can work with a 100 MHz clock, but we could not be sure. Can you clarify this?
2. I think FIR4, one of the FIR filters included in the product, is used to correct the inverse sinc within the band. An information can be given about the status when this filter is not used. We especially want to see the effect on image frequencies.
3. All charts in the Datasheet seem to be taken with an AC coupled measurement engine. A schematic showing the DC coupled output circuit status and measurement results etc. does it exist?

"

Thanks in advance

Best Regards

Furkan Sefiloglu

  • 0
    TI__Guru 69884 points

    Hi Furkan,

    Furkan Fehmi Sefiloglu said:
    As far as we understood from the DAC3484 graphics, it can work with a 100 MHz clock, but we could not be sure. Can you clarify this?

    Yes, the DACCLK can operate at 100MHz. The input data bus rate and DATACLK will need to be scaled accordingly with respect to the interpolation filters

    Furkan Fehmi Sefiloglu said:
    2. I think FIR4, one of the FIR filters included in the product, is used to correct the inverse sinc within the band. An information can be given about the status when this filter is not used. We especially want to see the effect on image frequencies.

    The inverse sinc filter will have a mirror image of gain (i.e. reverse spectrum) from Fs/2 to Fs. It also obey the Nyquist theorum.

    Furkan Fehmi Sefiloglu said:
    3. All charts in the Datasheet seem to be taken with an AC coupled measurement engine. A schematic showing the DC coupled output circuit status and measurement results etc. does it exist?

    All charts are taken with default 1:4 balun. The balun has a 20Mhz low frequency cutoff. We do not have any DC coupled measurements. Given the bias and compliance voltage are obeyed per the datasheet, the DC coupled performance will be the same as AC coupled. 

  • 0 in reply to Kang Hsia
    TI__Expert 3118 points

    Hi Kang,

    Can you please review the feedback and advise?

    "

    They wrote that we can achieve the same performance when the bias and compliance voltage in the datasheet are adjusted for DC coupled operation. According to the datasheet, we realized that only shunt resistors to ground would be sufficient. Can you ask to confirm?

    "

    Thanks in advance

    Best Regards

    Furkan Sefiloglu

  • 0 in reply to Furkan Fehmi Sefiloglu
    TI__Guru 69884 points

    Hi Furkan

    Please refer the customer to attached app note:

    https://www.ti.com/lit/pdf/slua647

    Yes, if no level translation is needed to interface to their downstream signal chain, then simple resistor termination to ground is sufficient. 

    -Kang