User's Manual

Page 17 of 31
Figure 2-10 The reference circuit of audio interface
1) The audio output signals, a pair of differential signals, output to two speaker. The output signal is not real stereo
signal which is different from traditional stereo sounds.
2) It is recommended to use the filter capacitor or filter circuit to reduce inter frequency interference and improve audio
quality. Just like what is shown in Figure 2-10.
3) To avoid static electricity, it is recommended to use the ESD protection device just like the varistors RV501, RV502
and RV503 in Figure 2-10.
4) It requires to connect audio analog signal ground with the general digital circuit ground, magnetic bead or zero ohm
resistance can be used just like R501 in Figure 2-10.
5) J501 is schematic diagram for four section of earphone jack, audio output signals connect with positive differential
signal and negative differential signal, audio input signals connect with positive differential signal only.
2.2.7 PCM interface and SPI interface
U6100 provides PCM and SPI interface by 60PIN board to board connector.