BitsyXb - User Manual
62
110118-0001A
6.3.8
Audio
For its audio sub-system the BitsyXb uses the Crystal CS4202 AC'97 stereo codec with dual audio
input and output channels. The BitsyXb adds an output power amplifier (National LM4863) and a
microphone pre-amp with power for electret microphones.
The output amplifier supports differential and single-ended modes. When the HP_IN signal is
greater than V HP_IN, the amplifier is in single-ended mode; when lower, it is in differential
mode.
The following diagram illustrates the relationship of the BitsyXb signal amplifiers to the codec:
+20dB
+20dB
MIC 1
Line_in_L
MIC 2
Line_in_R
+
-
+
-
Line_out_L
Line_out_R
CS4202
from power controller
HP_IN
The BitsyXb microphone circuitry can be factory configured to support "line in" inputs (1 Vrms
with no electret pull-ups) and different input gain and filtering. See section 6.1.4 for details about
volume production options.
Absolute Maximum Ratings
Vin_mic .................................................................... 5 Vdc
Symbol
Parameter
Min
Typ.
Max
Units
DVdd
codec digital supply voltage
3.3
V
Avdd
codec analog supply voltage
5.0
V
fso
sample rate, output
48
kHz
fsi
sample rate, input (note 31)
8
44.1
kHz
Audio Input
Vin_mic
signal input voltage
100
mV
rms
Gain_mic
pre-amp gain
20
dB
fo_mic
pre-amp low-pass cutoff (note 32)
3.4
kHz
Rin_mic
input impedance
12.5
k
Ω
Cin_mic
DC blocking capacitor
1
µ
F
Vmicpwr
microphone power (MIC_L/R+)
5
V
Rmicpwr
microphone power, series resistance
3.2
k
Ω
Audio Output
Rl
speaker load
4
8
Ω
Vout
Zspkr=4
Ω
, differential mode
3.7
V
rms
Vdc
DC bias, differential mode
0.5
Avdd
Pspkr
output power, ea. channel (note 33)
differential, THD+N 1%, Rl 4
Ω
1.0
2.2
W
differential, THD+N 10%, Rl 4
Ω
1.0
2.7
W
differential, THD+N 1%, Rl 32
Ω
1.0
0.34
W
single-ended, THD+N 0.5%, Rl 32
Ω
75
85
mW
single-ended, THD+N 1%, Rl 8
Ω
340
mW
single-ended, THD+N 10%, Rl 8
Ω
440
mW
