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ADS1299: Usage troubleshooting and performance evaluation

Ryan Wang
Prodigy 10 points
Part Number: ADS1299
Other Parts Discussed in Thread: ADS1292

Recently, we would like to use ADS1299 to design EMG acquisition circuit (technical specifications：0~600 μ V, 1~300Hz). I use a 3-electrode mode on the TI's evaluation kit (CH1P as LA, CH1N as RA, and BIAS_ELEC as RL), which can collect ECG signals from human body. It's the first step in the experiment, indicating that we have correctly used the TI's development kit.

According to the regulation standard, the resolution needs to be able to accurately collect sinusoidal signals of 10μV and 150Hz, and when the input signal changes by 2μV, the amplitude can be distinguished. The differential mode input impedance should be greater than 5MΩ, the common mode rejection ratio index needs to be greater than 100dB.

However, I found that these parameter of ADS1299 maybe can't match the regulation standard.
Test according to regulation standard, the signal input was connected to the TI's evaluation kit through the test circuit, and signal output and measurement through ADS1299EEG-FE software. However, the differential mode input impedance value was calculated to be smaller than 5MΩ. The common mode rejection ratio is about 60~80dB. Referring to the data manual, it can be seen that the minimum common-mode rejection ratio is 110dB; typical input impedance is 500MΩ.

Considering that TI's test conditions may be different from YY/T 1095 regulation standard, hope you can help me to evaluate whether it is correct to use ADS1299 to design the EMG acquisition circuit.
1. If the ADS1299 can meet the technical specifications, Are there any details in circuit design that need additional attention?
2. If the ADS1299 cannot meet the technical specifications, Is there any other more suitable circutit or chip recommended to realize the EMG acquisition device ?
Thanks.

  • 0
    TI__Mastermind 19815 points

    Hi,

    Unfortunately, we are not EMG experts and FYI, ADS1299 is not typically used for EMG application; however, we have seen people tried/attempted using either ADS1299 or ADS1292,4,6,8 from EMG application, so if the ADS1299 datasheet spec meet your application, please use evaluation board/kit(EVM) to evaluate, but support might be limited.

    -------------------------------------------------------------------------------------------

    1. When you say "regulation standard", may I ask what regulation standard are you referring to?

    2. For, "However, I found that these parameter of ADS1299 maybe can't match the regulation standard."   

    Don't know what "regulation standard" you are referring to, ADS1299 was not designed to by itself to "directly meet" any particular commercial product or medical devices standards/regulations, however, developers/customers can use ADS1299 in their product(s), and design product(s) that could meet the standards developers/customers want to meet.

    3.For "Considering that TI's test conditions may be different from YY/T 1095 regulation standard, hope you can help me to evaluate whether it is correct to use ADS1299 to design the EMG acquisition circuit."

    Comments: again the chip was not designed to meet/adhere any particular commercial product or medical devices standard, so it's customer responsibility to use the EVM to test/evaluate whether its suitable for the EMG applications.

    --------------------------------------------------------------------------------------------------------------------------------------------------------

    Also, there are very broad ranges/varieties of/for EMG applications, and each customer may have different needs, criteria and different standards they want to meet for their different products, so TI does not support each customer to meet any particular commercial and/or medical devices products standard/regulation.

    With this being said, it might be sufficient/suitable for some customers' needs or applications, but may not be sufficient/suitable for another.

    ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

    Unfortunately, we are not EMG experts and FYI, ADS1299 is not typically used for EMG application; however, we have seen people tried/attempted using either ADS1299 or ADS1292,4,6,8 from EMG application, so if the ADS1299 datasheet spec meet your application, please use evaluation board/kit(EVM) to evaluate, but support might be limited.

    Thanks

  • 0 in reply to ChienChun Yang
    Prodigy 10 points

    Hi, 

    thank you for your reply.

    According to the datasheet of ADS1299, the technical parameters of this chip meet the technical indicators that I need to achieve at present. But when I use the ADS1299 official evaluation kit circuit board and the ADS1299 official evaluation kit PC software for verification, the calculated CMRR is about 60~70dB, which is not near the 110dB value marked in the datasheet . I would like to ask you what are the possible reasons for this phenomenon?

  • 0 in reply to Ryan Wang
    TI__Mastermind 19815 points

    Hi,

    May I ask how exactly are customer's setup and tests to test, measure and calculate the CMRR?

    And, does customer set the configuration the same as the datasheet described? e.g.

    "AVDD – AVSS = 5 V, DVDD = 3.3 V, VREF = 4.5 V, external fCLK = 2.048 MHz, data rate = 250 SPS, and gain = 12 (unless otherwise noted)"

    "(2) CMRR is measured with a common-mode signal of AVSS + 0.3 V to AVDD – 0.3 V. The values indicated are the minimum of the eight channels."

    and what are the customer's common mode noises frequency and amplitude?

    ------------------------------------------------

    The following are the CMRR measurement/test method -

    The AC CMRR is tested with shorted input, and a 50/60Hz sine wave FS+/-0.3V signal is applied. Please refer to the datasheet note (2) for the test condition. The AC CMRR has a minimal value in the datasheet, so it is fully tested in the final production ATE test. And, results are shown in the datasheet.

    That is the info TI is allowed to shared/disclosed.

    Thanks.