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PCM1808-Q1: The purposes of the HPFs

Yoshikazu Kawasaki
Expert 3510 points
Part Number: PCM1808-Q1

Hello,

My customer was wondering the purposes of the following 2 HPFs.  Would you please give me your comments?

1. On-Chip High-Pass Filter:0.91Hz shown on top page of the datasheet.

   -> Is it for DC cut?

2. C1, C2: A 1-μF electrolytic capacitor gives 2.7 Hz (τ = 1 μF × 60 kΩ) cutoff frequency for the input HPF in normal operation shown on page 19.

   -> Why did you choose 2.7Hz for the cutoff frequency?

Best Regards,

Yoshikazu Kawasaki

  • 0
    TI__Guru 62625 points

    Hello,

    1.)  Yes, the low frequency ~0.91Hz high-pass cutoff is mostly to remove DC content from the input signals.

    2.)  Frequencies near 2Hz are common as it provides minimal attenuation over the audio band.  The customer can select this value to the frequency of their choice.