ADC3683EVM: LPF in the ADC3683EVM

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Part Number: ADC3683EVM
Other Parts Discussed in Thread: ADC3683

In the ADC3683EVM diagram, as shown by the left figure, there is an LPF(0~30 MHz) before the ADC3683. However, the datasheet (the right figure) of ADC3683 shows that the 3-dB bandwidth of ADC3683 is 900MHz. Does the LPF affect the ADC's performance if a signal with frequency larger than 30 MHz (such as 500 MHz) is sent to the AD3683EVM?

3 年多前

0 Kailyn Chen 3 年多前

TI__Guru**** 295050 points

Hello， I am sorry to reply you so late.

According to your questions, I think below post is similar with your question.

The use of the glitch filter (as you shared the image of above) is different from that of the AAF on the EVM. However, the glitch filter, in itself, acts as an AAF since it is really just a low pass filter. So, to ensure the ADC performs at its best, we recommend using the glitch filter topology first, and adding any additional filter components to that topology. With the EVM, you can test out what filter components/values will work best for your target application.

https://e2e.ti.com/support/data-converters-group/data-converters/f/data-converters-forum/1027261/adc3683-differential-input-impedance-for-simulating-aaf-and-glitch-filter/3797436#3797436

0 ?? ? 3 年多前

Thanks for the reply. Atfer reading the post, I'm still confused about the following questions:

(1) Is the glitch filter installed before the sampling circuit? If it is, then, how can the glitch filter absorb the glitch from the sampling operation?

(2) Does the glitch filter have effect on the 3-dB bandwidth (900 MHz)？

+1 ?? ? 3 年多前回复 Kailyn Chen

Thanks for the reply. Atfer reading the post, I'm still confused about the following questions:

(1) Is the glitch filter installed before the sampling circuit? If it is, then, how can the glitch filter absorb the glitch from the sampling operation?

(2) Does the glitch filter have effect on the 3-dB bandwidth (900 MHz)？

0 Kailyn Chen 3 年多前回复 ?? ?

TI__Guru**** 295050 points

1. It installed before ADC input to avoid glitch when sample.

2, The datasheet described the bandwidth could get to 900Mhz, it means at 900MHz, the signal could still be sampled. But according to different application, it requires different Nyquist zone. Users could design bandpass filter or low pass filter for different uses case. However, due to roll-off of the analog bandwidth, there will be distortions and performance degradations.

As to the input filter of ADC, we have a FAQ which describes detail about" Delta-sigma ADC anti-aliasing filter component selection":

https://e2e.ti.com/support/data-converters-group/data-converters/f/data-converters-forum/955466/faq-delta-sigma-adc-anti-aliasing-filter-component-selection

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ADC3683EVM: LPF in the ADC3683EVM