Specifications

41
Figure 15: ADC analogue amplifier block diagram
The second stage of the analogue amplifier shown in Figure 15 has a programmable gain
with seven individual 3dB steps. In simple terms, by combining the 24dB gain selection of
the microphone input with the seven individual 3dB gain steps, the overall range of the
analogue amplifier is approximately -3dB to 42dB in 3dB steps. The overall gain control of
the ADC is controlled by a VM function. See iWRAP user guide how to set the gain using
iWRAP commands.
7.2.2 DAC
The DAC consists of two third-order Sigma Delta converters allowing two separate
channels that are identical in functionality as shown in Figure 14.
Each DAC supports the following samples rates:
 8kHz
 11.025kHz
 16kHz
 22.050kHz
 24kHz
 32kHz
 44.1kHz
 48kHz
See the iWRAP user guide how to set the sampling rate using iWRAP commands. The
default setting for A2DP is 44.1 kHz and for HFP 8 kHz.
The DAC contains two gain stages for each channel: a digital and an analogue gain stage.
The digital gain stage has a programmable selection value in the range of 0 to 15 with
associated DAC gain settings. This is summarised in Table 14. There is also a high
resolution digital gain mode that allows the gain to be changed in 1/32dB steps. Please
contact Bluegiga Technologies for more information.
Gain Selection Value ADC Digital Gain Setting (dB)
0 0
1 3.5
2 6