9.2.4
ADC Audio Input Gain
Figure 9.3 shows that the CSR8640 BGA audio input gain consists of:
■
An analogue gain stage based on a pre-amplifier and an analogue gain amplifier, see Section 9.2.5
■
A digital gain stage, see Section 9.2.6
G-
TW
-00
05535.4.3
ADC Pre-amplifier
and ADC Analogue Gain:
-3dB to 42dB in 3dB steps
ADC Pre-amplifier:
0dB, 9dB, 21dB and 30dB
ADC Analogue Gain:
-3dB to 12dB in 3dB steps
ADC Digital Gain:
-24dB to 21.5dB in alternating
2.5dB and 3dB steps
Audio Input
To Digital Codec
System Gain = ADC Pre-amp ADC Analogue Gain + ADC Digital Gain
Figure 9.3: Audio Input Gain
9.2.5
ADC Pre-amplifier and ADC Analogue Gain
CSR8640 BGA has an analogue gain stage based on an ADC pre-amplifier and ADC analogue amplifier:
■
The ADC pre-amplifier has 4 gain settings: 0dB, 9dB, 21dB and 30dB
■
The ADC analogue amplifier gain is -3dB to 12dB in 3dB steps
■
The overall analogue gain for the pre-amplifier and analogue amplifier is -3dB to 42dB in 3dB steps, see
■
At mid to high gain levels it acts as a microphone pre-amplifier, see Section 9.2.13
■
At low gain levels it acts as an audio line level amplifier
9.2.6
ADC Digital Gain
A digital gain stage inside the ADC varies from -24dB to 21.5dB, see Table 9.2. There is also a
fine gain interface
with a 9-bit gain setting allowing gain changes in 1/32 steps, for more infomation contact CSR.
The firmware controls the audio input gain.
Advance Information
This material is subject to CSR's non-disclosure agreement
© Cambridge Silicon Radio Limited 2011
Page 39 of 110
CS-209182-DSP1
CSR8640 BGA
Data Sheet
