at85c51snd3 ATMEL Corporation, at85c51snd3 Datasheet - Page 155

• Manufacturer Part Number: at85c51snd3
• Description: At85c51snd3 Single-chip Digital Audio Decoder - Encoder With Usb 2.0 Interface
• Manufacturer: ATMEL Corporation

Output Drive Control
Audio Inputs
Inputs Sources
Audio Input Preamplifier Gain
7632D–MP3–01/07
Table 157. Audio Codec Output Gain
Output buffers can operate in two modes depending on the power supply voltage. These
are low impedance or high impedance modes. The low impedance mode is only avail-
able in high power supply configuration and allows to drive a typical 32 Ω stereo
headphone, while the high impedance mode is available in low or high voltage power
supply configurations and allows to drive a typical 50 KΩ stereo amplifier. Control is
done by setting or clearing AODRV bit in ACCON according to Table 158.
Table 158. Audio Codec Output Drive Selection
The audio input system is based on a single sigma-delta A/D converter provided for
mono recording. It is enabled by setting the AIEN bit in ACCON.
Audio input system features are detailed in the following sections.
The audio input source can come from either an electret type microphone input or the
stereo lines inputs sources. The selection of the source is done by setting or clearing the
AISSEL bit in ACCON according to Table 159. When line inputs are selected as audio
input source, stereo channels are combined together in a mono signal prior to feed the
preamplifier.
Table 159. Audio Codec Input Source Selection
The signals coming from audio inputs goes through a preamplifier to adapt levels prior
to feed the A/D converter.The preamplifier gain is controlled by AIPG2:0 bits in ACIPG
according to Table 160.
Table 160. Audio Codec Input Preamplifier Gain
AORG4:0
AOLG4:0
AIPG2:0
00000
00001
00010
00011
00100
00101
00110
000
AODRV
AISSEL
0
1
0
1
Gain Value
6 dB
4 dB
2 dB
0 dB
-2 dB
-4 dB
-6 dB
Gain Value
0 dB
Drive Selection
Low/high voltage 50 KΩ drive
High voltage 32 Ω drive
Selection
Line Inputs
Microphone Input
AORG4:0
AOLG4:0
AIPG2:0
01000
01001
01010
00111
01011
01100
01101
010
Gain Value
-8 dB
-10 dB
-12 dB
-14 dB
-16 dB
-18 dB
-20 dB
Gain Value
+12 dB
AORG4:0
AOLG4:0
AIPG2:0
≥ 10011
10000
10001
10010
01110
01111
100
Gain Value
-22 dB
-24 dB
-26 dB
-28 dB
-30 dB
Mute
Gain Value
+24 dB
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