PCM1808： VDD of speaker out is over Analog input voltage of PCM1808

kaipeng chu

Part Number: PCM1808
Other Parts Discussed in Thread: PCM6240-Q1

Hi Sir,

I attached our audio DSP/AMP/ADC converter block diagram.
The power in of the class D AMP is 20V, so the VDD of speaker out is 10V that is over the analog input power of PCM1808.
Does the VinL/R spec of the converter exceed 10V? Is there a recommended model?
Or recommend a RC circuit can be add in front of the analog input that does not exceed VinL/R spec.

B.R.
Ken

over 4 years ago

0 Collin Wells over 4 years ago

TI__Guru 62625 points

Hello,

The PCM1808 has absolute maximum input ratings of -0.3V to VCC +-0.3V (up to +5V) as shown in Section 6.1 of the datasheet. If you exceed these levels you will damage the PCM1808.

You will need an external passive attenuator to reduce the signal levels into the PCM1808. This can be as simple as a resistor divider.

Alternatively, consider the PCM6240-Q1 device, it has a built-in attenuator.

0 kaipeng chu over 4 years ago in reply to Collin Wells

Prodigy 250 points

Hi Collin,

Is there a recommended value for the R1/R2 of this passive attenuator circuit for this PCM1808

I mean the range of R1/R2 value, 5K ohm is OK?

BR Ken

0 kaipeng chu over 4 years ago in reply to kaipeng chu

Prodigy 250 points

Hi Collin,

Update the passive attenuator circuit.

The atenuation factor is 0.457 and the VCC of PCM1808 is 5V.

Could you help check it?

Thanks.

B.R.

Ken

0 kaipeng chu over 4 years ago in reply to kaipeng chu

Prodigy 250 points

Hi Collin,

The audio amp model we use is TAS5825MRHBR, do we can use PCM1808?
or need to add Audio Line Driver between PCM1808 and TAS5825MRHBR

B.R.

Ken

0 Collin Wells over 4 years ago in reply to kaipeng chu

TI__Guru 62625 points

Hi Ken,

The circuitry you showed in the previous post will work properly with the PCM1808 and a 10V input signal. The input impedance of 60k will interact with the passive attenuator creating a slight gain error, but since you're already shifting the transfer function, this can be further tuned during production.

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PCM1808： VDD of speaker out is over Analog input voltage of PCM1808