Specifications

Bluegiga Technologies Oy
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4
1.95
0.480
5
2.02
0.530
6
2.10
0.610
7
2.18
0.670
8
2.32
0.750
9
2.43
0.810
A
2.56
0.860
B
2.69
0.950
C
2.90
1.000
D
3.08
1.090
E
3.33
1.140
F
3.57
1.230
Table 21: MIC_BIAS settings in iWRAP
9.1.4 Line Input
Line input mode is selected by setting the ADC preamplifier off (see chapter 9.1.1). In the line input mode the
input impedance varies from 6k to 30 kohm depending on the gain setting.
Figure 19 and Figure 20 show examples of line input connection with WT32i. The maximum line level rms
voltage can vary from 0.3 up to 1.6 Vrms depending on the application, while the maximum for WT32i is
0.4Vrms (0.8Vrms differential). Thus it may be necessary to use a voltage divider (R1 and R2) at the input to
attenuate the incoming signal. C1 and C2 are typically 1uF ceramic X7R or film type capacitors.
It is a good practice to place a LC (22nH + 15pF) filter close to each input to filter out any RF noise that might
couple to the audio traces.
R1
R2
C1
C2
WT32i
AUDIO_IN_N_LEFT
AUDIO_IN_P_LEFT
Line input
Figure 19: Single ended line input example