The overall gain control of the DAC is controlled by the firmware. Its setting is a combined function of the digital and
analogue amplifier settings.
Digital Gain Selection
Value
DAC Digital Gain Setting
(dB)
Digital Gain Selection
Value
DAC Digital Gain Setting
(dB)
0
0
8
-24
1
3.5
9
-20.5
2
6
10
-18
3
9.5
11
-14.5
4
12
12
-12
5
15.5
13
-8.5
6
18
14
-6
7
21.5
15
-2.5
Table 9.3: DAC Digital Gain Rate Selection
9.2.11
DAC Analogue Gain
Table 9.4 shows the DAC analogue gain stage consists of 8 gain selection values that represent seven 3dB steps.
The firmware controls the overall gain control of the DAC. Its setting is a combined function of the digital and analogue
amplifier settings.
Analogue Gain Selection
Value
DAC Analogue Gain
Setting (dB)
Analogue Gain Selection
Value
DAC Analogue Gain
Setting (dB)
7
3
3
-9
6
0
2
-12
5
-3
1
-15
4
-6
0
-18
Table 9.4: DAC Analogue Gain Rate Selection
9.2.12 DAC Digital FIR Filter
The DAC contains an integrated digital FIR filter with the following modes:
■
A default
long
FIR filter for best performance at ≥ 44.1kHz.
■
A
short
FIR to reduce latency.
■
A
narrow
FIR (a very sharp roll-off at Nyquist) for G.722 compliance. Best for 8kHz / 16kHz.
Advance Information
This material is subject to CSR's non-disclosure agreement
© Cambridge Silicon Radio Limited 2011
Page 41 of 110
CS-209182-DSP1
CSR8640 BGA
Data Sheet
