PCM1753-Q1: Help needed on LPF circuit for Left and Right Channels

Amrit Pal

Prodigy 10 points

Part Number: PCM1753-Q1

Dear TI Team,

Please help me with review of the below schematic and as well as help to share the circuit for LPF for both channels.

over 2 years ago

0 Jeff McPherson over 2 years ago

TI__Mastermind 33840 points

Hi Amrit,

The only issue I can see immediately is that you are not using VCOM to bias the signal. Because you have AC coupled the output, and not used VCOM as a bias, your output is centered at 0V, which will clip with the negative rail (GND). I would remove C40 and C45 and use VCOM to bias the output. This can be done with a relatively large resistor connected to the output, or you can refer to the datasheet (8.3.6.1) or Application Note https://www.ti.com/lit/an/sbaa322/sbaa322.pdf?ts=1648490883335&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FPCM1753-Q1 for some ideas there.

0 Amrit Pal over 2 years ago in reply to Jeff McPherson

Prodigy 10 points

Hi Jeff,

If I refer to the datasheet (8.3.6.1) for LPF sections for both right and left side, do you have the exact values of the Capacitors and resistors or any reference circuit with calculations.

0 Jeff McPherson over 2 years ago in reply to Amrit Pal

TI__Mastermind 33840 points

Hi Amrit,

I can't tell you what the "exact values" are because it depends on what your goals/constraints are. The filter shown in the datasheet is a multiple feedback active low pass filter. This website has a tool to simulate ideal situations of this filter (along with many others) :http://sim.okawa-denshi.jp/en/Fkeisan.htm You could also use the same website to model the Sallen-Key architecture that you already have.

Best regards,

Jeff

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PCM1753-Q1: Help needed on LPF circuit for Left and Right Channels