Other Parts Discussed in Thread: PCM3070
Sorry if the question may seem lame but I am a beginner and I need help. I am making a custom board with PCM3070 as an adder. I am posting a snapshot of the PCM3070K_CS ( even though I am not using it for making my doubt clearer )
I am selecting the inputs that are underlined in red. So my doubt is, in this particular configuration what is the output that will got to MAL ? Will it be IN1_L + IN2_L + IN1_R (+ IN2_R) or( -IN2_R).
thanks in advance.
Hi Rohit:
The output will be the IN1_L + IN2_L + IN1_R - IN2_R. So you want to do mix at the input? If the IN1_L and IN1_R is differential signal, the output will be IN2_L - IN2_R, because the IN1_L+IN1__R will be zero.
Usually, we configure the input like this:
Hi Derek,
Thanks for the reply. I am giving four separate audio inputs which have to be mixed. So assuming I give the inputs through IN1_L, IN2_L,IN3_L and IN1_R all can be mixed at the input? The signals are not differential.
and one more doubt is that do I need to connect the CM for enabling my configuration? I hope you understood my question.
Regards,
Rohit.
Hi Rohit:
You can mix them. But you should add common mode voltage(CM). Because at the positive input of PGA it will also have common mode voltage. We must connect the CM to make sure the output will no common mode voltage. And be careful one thing. If the signals which you want to mix is too big. You should choose another resister like 20K ,40K to avoid overflow.
Hi Rohit:
Sorry for the delay. In fact the CM1L and CM2L are same. Why do we have two CMs is that we need balance the negative and positive impedance.
Below is an example.
