PCM1808: PCM1808 - Frequency response not linear

Gabriel Boucher

Part Number: PCM1808
Other Parts Discussed in Thread: PCM1803

Hi,

Is the PCM1808 frequency response supposed to be linear up to 20 kHz?

I'm taking measurements and there's a slight attenuation starting at 6 KHZ down 1dB at 20Khz. (please see the attached image)

Any idea what could cause this?

thanks

Gabriel

over 4 years ago

0 Zak Kaye over 4 years ago

TI__Mastermind 23050 points

Hi Gabriel,

The PCM1808 should have a flat frequency response. Unfortunately your image did not come through. Can you try reposting and include your schematic as well?

Best,

Zak

0 Gabriel Boucher over 4 years ago in reply to Zak Kaye

Prodigy 40 points

Hi Zak,

turns out the input needed proper buffering. I also added an active LPF filter and the frequency response is pretty flat.

Quick question... Which ADC from the 18xx series should I choose? I have tested the PCM1803 and PCM1808 and both gave similar results.

Thanks

0 Zak Kaye over 4 years ago in reply to Gabriel Boucher

TI__Mastermind 23050 points

Hey Gabriel,

Glad you were able to resolve the issue. The best device to choose really depends on your requirements and system constraints. Some of the device in the family have differential inputs with higher performance so it just depends what your key careabouts are.

Best,

Zak

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PCM1808: PCM1808 - Frequency response not linear