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ADC12D1620QML-SP: DESIQ vs. DESI vs. DESQ Performance

John Roy94
Prodigy 180 points
Part Number: ADC12D1620QML-SP

Good morning, 

In the datasheet for the ADC12D1620QML-SP device, Table 7 outlines the performance difference between the various modes of the device (DESI/Q, DESIQ, DESIQCLK). However, there are no performance charts in the datasheet that show the various performance curves for DESI mode. 

Does this information exist somewhere? We need a more quantitative measure to evaluate what mode we should use the device in. The missing data for DESI (or DESQ) mode needs to be understood for SFDR. Table 7 indicates that DESI (or DESQ) mode has the highest SFDR performance with the lowest input bandwidth. What does this mean? 

Regards,

John

  • 0
    TI__Intellectual 2750 points
    Hello John,
    I have sent your question to an engineer that can take a look at what else we have on the ADC12D1620 device.
    Regards,
    Brian
  • 0 in reply to Brian2001
    TI__Mastermind 43930 points

    Hi John

    A number of the Typical Characteristics Figures include performance for DES mode. (See the Red curve in Figure 13 - Figure 30).

    This information is applicable for either DESI or DESQ mode of operation.

    This document (http://www.ti.com/general/docs/lit/getliterature.tsp?literatureNumber=tidu175&fileType=pdf) helps explain the ADC input mux configurations for the different non-DES and DES sampling modes. The DESI and DESQ modes have the best signal path matching from ADC input to internal I-channel and Q-channel converters. This minimizes interleaving spurs caused by amplitude, offset and timing errors and gives the best SFDR performance. Unfortunately this input mode has relatively higher parasitic loading on the input signal, resulting in reduced input bandwidth compared to the non-DES modes and the other DES modes (discussed next).

    DESIQ and DESCLKIQ have relatively lower parasitic loading but worse signal path matching. The reduced loading results in higher input bandwidth performance, but the degraded matching causes increased interleaving spurs and reduced SFDR performance compared with DESI or DESQ modes.

    I hope this is helpful.

    Best regards,

    Jim B