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ADS9219: Technical Query Regarding ADS9219

charan Raj
Prodigy 40 points

Part Number: ADS9219

Tool/software:

We are currently evaluating the ADS9219 ADC. We would appreciate clarification on the following points based on the datasheet, 

  1. LVDS Output Structure:
    The datasheet mentions that each channel outputs 48 bits, consisting of 24-bit I and 24-bit Q data from the digital mixer. However, from the LVDS output waveform, we observe only 24 bits per channel.       Figure 6-1 and Figure 7-5:

    • Could you please clarify whether the full 48-bit data is transmitted sequentially?

    • How is the I/Q data structured and serialized on the LVDS interface?

  2. According to the datasheet, the full-scale differential input range is –3.2 V to +3.2 V, which corresponds to 6.4Vpp Single ended signal or 6.4Vpp Differential swing 

    • With a 50-ohm shunt resistor added externally (since the ADC has a high input impedance due to its internal buffer), this would translate to approximately +19 dBm of input power. Please confirm if this understanding and calculation are correct

  3. Single-Ended Drive Feasibility:
    While the ADS9219 includes an internal differential driver, the datasheet also recommends using an external differential driver for single-ended sources.

    • Is it possible to directly drive the ADC with a single-ended signal with 50Ohm shunt resistor?

  • 0
    TI__Expert 8490 points

    Hello Charan Raj, 

    Welcome to TI's E2E Forum! I am happy to hear the ADS9219 is being evaluated. 

    To answer your questions: 

    1. The data for for the mixer output is 48-bits: {I data [23:0],Q Data[23:0]} in one frame clock period. Being that the Down Converter requires decimation to also be enabled, the output data rate is reduced accordingly. Meaning that with the minimum decimation (2) the frame clock (FCLK) will be 2x the sample clock, allowing for the 48-bit frame.

    2. Yes, your understanding is correct, The ±3.2V input range refers to a 6.4Vpp differential input, with the max delta between AINxP - AINxM is 3.2V and the min -3.2V.

    3. No, the ADS9219 require a differential input, even with the internal driver. So for single-ended sources an external differential driver is recommended. 

    If I may ask the use case for the single-ended + mixer/NCO? is there a preferred single-ended driver/op-amp that is already in place? 

    Also, we do also have a 1-ch version of this device that is about to be released if that is of interest? 

    Best regards, 

    Yolanda