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ADS127L01: Selection of A/D-converter

Gerald
Genius 9580 points
Part Number: ADS127L01
Other Parts Discussed in Thread: ADS127L11, ADS1260-Q1, ADS1260

Hi Experts,

May I ask for help? Our customer is in advance development project, they are detecting specific forces of the steering system in their cars. Those sigals get amplified by a measuring amplifier. We are looking for an A/D-converter which converts the analog output of the measuring amplifier of +-10V into a digital signal. It should sample in 24 bit solution at a rate of 20 kHz. Can you suggest an fitting ADC for this application?

I am checking ADS127L01 but not sure if this can still fit for this application and this is also not available. Please advise if you know a device that could fit. Thank you so much.

Kind regards,
Gerald 

  • 0
    TI__Mastermind 39510 points

    Hello Gerald,

    I suggest looking at the ADS127L11, which is the next generation ADS127L01 device.  ADS127L11 can support higher data rates and includes pre-charge amplifiers for the ADC input and reference, which eases drive requirements.  With either device, you will need an input amplifier to level shift the +/-10V and drive the ADC inputs.  ADS127L11 released at the end of last year and stock is available.

    Another option that may be a better fit is ADS1260-Q1, which is rated for automotive applications.  This device includes an internal PGA, current source, and supports data rates up to 40ksps.  This device is ideal for measuring bridge sensors.

    Regards,
    Keith Nicholas
    Precision ADC Applications

  • 0 in reply to Keith Nicholas
    TI__Genius 9580 points

    Hi Keith,

    Please be informed that customer have another question regarding the level shift.
    It would be possible to set the amplifier output to 0 ... 5V, so then would he not need an level shift right?

    He would use 3 of the 5 channels of the ADS1260-Q1.
    Does it affect the sampling rate per chanel?
    So would he have a sampling rate per chanel of 40 ksps / 3 = 13,3 ksps?

    Thank you and kind regards,
    Gerald

  • 0 in reply to Gerald
    TI__Mastermind 39510 points

    Hi Gerald,

    Correct, the AINx inputs of ADS1260 can accept an input voltage from 0 to 5V with respect to GND.  In order to take advantage of the full scale input range, the internal reference voltage Vref=2.5V can be used.  Connecting Vref=2.5V to the AINCOM pin with AINx from 0V to 5V, the ADC differential voltage will now range from -2.5V to +2.5V, which is the full scale input range of the ADC when using Gain=1.

    When using the multiplexor to scan channels, there is an additional delay to allow the internal digital filter to fully settle.  In this case, the data period is increased quite a bit, resulting in a much slower data rate per channel.

    Referring to Table 8 in the ADS1260-Q1 datasheet, the conversion latency for the 40ksps data rate is 179usec.  This is the effective data period when using the multiplexor to scan channels, resulting in an effective data rate of 1/179usec=5.5ksps.  As a result, the sampling rate per channel (for 3 channels) will now be 5.5ksps/3=1.8ksps.

    What is the desired sample rate per channel, with a total of 3 channels?  Please note that if a single channel is used, then you can get the full 40ksps for a single channel.

    Regards,
    Keith