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AFE58JD18: Filter Parameters, Signal amplification and Digital TGC

Nidhal Mansoor
Prodigy 130 points
Part Number: AFE58JD18

Hi,

  1. What is the filter order and characteristics of LNA HPF?
  2. What is the filter order and characteristics of PGA HPF?
  3. It is mentioned in datasheet that PGA LPF is a third order filter with Butterworth characteristics and a typical 18-dB per octave roll-off. Suppose I am running the ADC(in 14 bit) at 20 MHz and LPF cut-off is at 10 MHz. Will it act as an anti-aliasing filter? The attenuation at 20 MHz will only be 36-dB. As per my understanding a 14-bit ADC needs at least 84 dB attenuation before Fs/2 (here 20/2 = 10 MHz). Correct me if I am wrong. Do I need to use any external filters?
  4. I am using this AFE58JD18 for sonar application. It has two frequencies of operation: 1: 105kHz with 20 kHz Bandwidth and 2: 500kHz with 50kHz bandwidth. The input signal to AFE ranges from 215 nVpp to 4 mVpp approx. Do I need to use external pre amplifier for amplifying this signal or AFE58JD18 is sufficient?
  5. I am planning to implement Digital TGC. I will adjust the VCAT attenuation from 42dB to 0 dB in 6-dB steps for each scan through SPI. Correct me if I am wrong. What to do with AFE TGC pins if I am implementing Digital TGC.
  6. Is there any document mentioning how to calculate noise level introduced by AFE?

Thanks,

Nidhal