TI中文支持网Part Number:ADS8881
Hi,
I am designing a data acquisition system base on ADS8881 to capture a sine wave signal from 0 ~100kHz(differential signal), my signal source is a little noisy, so I need to add an external low pass filter to achieve the best dynamic performance of ADS8881, my question is which type of low pass filter is the best chose for ADS8881 to achieve best SNR & THD in this application? I am thinking to use high order RLC low pass filter or MFB low pass filter, or is there other better solution? Is it possible to achieve the ADS8881 datasheet performance(100dB SNR, -115dB THD) in this application ? Please help!
Below is the FFT of my signal source.
Kailyn Chen：
Hello, thank you very much for your support of TI.
About your questions, I would forward it to our engineer who will contact you and support your question.
,
Kailyn Chen：
Hello， about your questions, please refer to the below reply:
Please point them to the Application Section of the ADS8881 data sheet. We have several signal chain suggestions that are optimized for various input signal types and performance targets. What does their input circuit look like today?
In addition, noise can come from other sources besides the input signal source. How do they know that the noise in the figure above is coming from the source and not from other active components? Noise could also be caused by PCB layout, power supplies, reference voltage, etc. In general, a low-pass filter is not always the solution because it depends on how the noise is coupling into the ADC.
The ADS8881 has a low input impedance that connects directly to a switch-capacitor sampling network. Therefore, low inductance is important when designing an input circuit for this type of ADC. I don't believe an RLC filter is a good choice for this device, so perhaps an MFB amplifier circuit is a good starting point.
