PCM1851A: what to do with unused Vin pins of PCM1851A

rifo

Expert 1105 points

Part Number: PCM1851A

Hello,

What should I do with the unused Vin pins of PCM1851A? I wasn't able to find this information in the datasheet.

thanks

over 8 years ago

0 Diego Melendez over 8 years ago

TI__Guru 57800 points

Hi, Rifo,

In general, unused ADC inputs should be AC-coupled to ground due to the DC offset present on the input pins.

Best Regards,

-Diego Meléndez López
Audio Applications Engineer

0 rifo over 8 years ago in reply to Diego Melendez

Expert 1105 points

hello, thanks

what value should we use then for the capacitor? Is there a common value that is used?

0 Diego Melendez over 8 years ago in reply to rifo

TI__Guru 57800 points

Hi, Rifo,

In general, using the same values of the recommended caps for the input lines should be fine (0.33µF for the PCM1851A).

Best Regards,

-Diego Meléndez López
Audio Applications Engineer

0 rifo over 8 years ago in reply to Diego Melendez

Expert 1105 points

Hello,

Something came to my attention. On PCM1851A datasheet page 16, there is the below statement.

"All unselected channel inputs are terminated VrefS (= 0.5 Vcc) using a resistor, typically 57kohm"

Is this something that is done in PCM1851A itself? we don't need to place any resistors right?

0 Diego Melendez over 8 years ago in reply to rifo

TI__Guru 57800 points

Hi, Rifo,

This device accepts the use of a terminating resistor connected to VrefS as an option, Using a cap to AC couple to GND is a common technique that also can be used for this device. The effect should be the same for either case.

Best Regards,

-Diego Meléndez López
Audio Applications Engineer

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PCM1851A: what to do with unused Vin pins of PCM1851A