PCM1821: Connection Recommendation for Unused Analog Inputs

Chris Read

Part Number: PCM1821
Other Parts Discussed in Thread: PCM1822-Q1, PCM1820, PCM1820-Q1

If only one channel of the PCM1821 analog input pair is needed, what is the recommended connection for the other pair?

Does this same recommendation apply to PCM1820, PCM1820-Q1, PCM-1821-Q1, and PCM1822-Q1 as well?

I also submitted feedback to the datasheet documentation recommending that this should be added there.

There are recommendations on e2e.ti.com for other ADC parts in the TI catalog, but they aren't all consistent, so a specific answer for these parts would be appreciated.

Thanks in advance,

Chris

over 1 year ago

+1 Jeff McPherson over 1 year ago

TI__Mastermind 32180 points

Hi Chris,

Sorry for the confusion. You may have come across this e2e post: https://e2e.ti.com/support/audio-group/audio/f/audio-forum/773066/faq-audio-adcs-codecs-what-should-i-do-with-unused-inputs-on-the-tlv320adc-and-tlv320aic-family-of-devices

Even though it doesn't mention the PCM182x family, the advice is still valid in general for our audio ADC's and codecs. You can AC couple to ground unused inputs to prevent the inputs from picking up noise. We recommend 0.47uF as a rule of thumb, but you can chose the capacitor value that is best for you by selecting a capacitor that can hold the DC bias on the input pins, and if necessary, has a capacitance that creates a desirable high pass filter with the input impedance.

Best regards,

Jeff McPherson

Audio

Audio forum

PCM1821: Connection Recommendation for Unused Analog Inputs