CMX649 Просмотр технического описания (PDF) - CML Microsystems Plc
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CMX649 Datasheet PDF : 50 Pages
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ADM Codec
CMX649
4. External Components
C1
C2 R2
C6
MIC
R1
C4 R4
R3
C3
C5
C7
STRB
1
ENCODE VAD
2
VDD
3
MIC OUT
4
MIC+
5
MIC-
6
VBIAS
7
AUDIO OUT
8
VSS
9
DECODE VAD
10
CMX649E3
TX DATA
20
TX CLK
19
CSN
18
SCLK
17
CMD
16
RPLY
15
IRQN
14
XTAL/CLK
13
RX CLK
12
RX DATA
11
µC
INTERFACE
X1
Figure 2 Recommended External Components
R1, R2
R3, R4
C1, C3
C2, C4
Note 1
Note 1
Note 1
Note 1
100kΩ
100kΩ
100 pF
0.01µF
±10%
±10%
±20%
±20%
C5 Note 2 33.0µF
±20%
C6 Note 3 1.0µF
±20%
C7 Note 4 1.0µF
±20%
X1 Note 5 4.096MHz
Notes:
1. C1 - C4 and R1 - R4 set the microphone amplifier gain and frequency response. The values
shown set the gain to unity and the low and high –3 dB frequency rolloff points to approximately
150Hz and 15kHz respectively.
2. DC blocking capacitor for driving a speaker from an external speaker amplifier. The value shown
is based on a 32Ω impedance speaker where the highpass rolloff frequency is set to
approximately 150Hz.
3. VDD decoupling capacitor.
4. Bias decoupling capacitor.
5. A 4.096MHz Xtal/Clock input will yield exactly 16kbps/32kbps/64kbps internally generated data
clock rates.
6. To achieve good noise performance, VDD and VBIAS decoupling and protection of the signal path
from extraneous in-band signals are very important. It is recommended that the printed circuit
board is laid out with a ground plane in the CMX649 area to provide a low impedance connection
between the VSS pin and the VDD and VBIAS decoupling capacitors.
© 2003 CML Microsystems Plc
5
D/649/2
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