7.3.7 Differential Inputs

The differential input stage of the amplifier cancels any noise that appears on both input lines of the channel. To use the TPA31xxD2 family with a differential source, connect the positive lead of the audio source to the RINP or LINP input and the negative lead from the audio source to the RINN or LINN input. To use the TPA31xxD2 family with a single-ended source, ac ground the negative input through a capacitor equal in value to the input capacitor on positive and apply the audio source to either input. In a single-ended input application, the unused input should be ac grounded at the audio source instead of at the device input for best noise performance. For good transient performance, the impedance seen at each of the two differential inputs should be the same.

The impedance seen at the inputs should be limited to an RC time constant of 1 ms or less if possible. This is to allow the input dc blocking capacitors to become completely charged during the 10 ms power-up time. If the input capacitors are not allowed to completely charge, there will be some additional sensitivity to component matching which can result in pop if the input components are not well matched.