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ADS1605: availability (new design consideration) and 2xmode

Xavier Queffelec
Intellectual 310 points
Part Number: ADS1605
Other Parts Discussed in Thread: ADS1606,

Dear Community,

I am looking for an ADC for a new application with 16 bits and a low INL (< +/- 1) and at least 2.5MSPS better 5MSPS

I found the ADS1605 and ADS1606 which are matching these criteria.

As I saw on the datasheet that this ADC was designed in 2003 - will you recommend it for a new design?

How long will this part be available in the future?

In this part there is also a nice feature - the 2xmode - as I reed the datasheet this mode reduce the resolution to 14bits.

How does it look like in this mode with the INL error - Does it remains or what is the new value?

With this feature I will be able to get better information on the input signal I have, but I need to keep low noise.

A last question: for metrology application, where linearity and low noise are important, what it is better to choose: SAR or delta-sigma architecture?

Many thanks for your help,

Best Regards,

Xavier

  • 0
    TI__Guru 60346 points

    Hello Xavier,

    Thanks for your interest in our ADS1605!

    Firstly, we have no plans to remove the ADS1605 from our portfolio. It is certainly still recommended for new designs today and will continue to be supported by our product line.

    Regarding the linearity performance, I would expect INL to remain the same in 2X Mode. The only thing that's changing in 2X Mode is the oversampling ratio (OSR). When 2XMODE is high, the OSR reduces from 8 to 4, effectively doubling the output data rate. The master CLK and input sampling rate, however, remain the same. INL has more of a dependency on the input sampling rate rather than the decimation ratio used in the digital filter.

    The datasheet section on 2X Mode explains some of the performance differences between Normal Mode and 2X Mode. SNR will get worse by about 14 dB, but THD remains approximately the same. Since INL is strongly correlated to THD, I feel confident that INL is not expected to degrade in 2X Mode.

    For more information on using the ADS1605 in 2X Mode, please read the following app note:

    www.ti.com/lit/pdf/slaa180

    As far as which ADC architecture you choose, there are a lot of generic differences that can help you make that decision. The main benefits of the delta-sigma is the built-in noise-shaping and decimation, which improves overall noise performance in the bandwidth of interest. The digital filter frequency response also provides you with at least 72 dB of stopband attenuation between the filter passband and the modulator sampling frequency. This makes designing your antialiasing filter a little easier. If you don't need to control the precise beginning/end of each sample and you can allow the converter to run freely, delta-sigma's may make sense for your application.

    The downside to the ADS1605 is probably its power consumption and size. The package body is 10mm x 10mm and typical power consumption is around 570 mW. You might be able to find a SAR ADC which can achieve the same 14-bit resolution in a smaller package and lower power.

    Best Regards,

  • 0 in reply to Ryan Andrews
    Intellectual 310 points

    Dear Ryan,

    Many thanks for your answer.

    I will take care about your remark concerning power consumption and size.

    I will also compare it with your SAR to see, which solution is the best for us.

    Best Regards,

    Xavier