W682510_05 Datasheet, PDF (8/35 Pages) Winbond – DUAL-CHANNEL VOICEBAND CODECS

W682510/W682310
7. FUNCTIONAL DESCRIPTION
W682510/W682310 is a single-rail, dual channel PCM CODEC for voiceband applications. The
CODEC complies with the specifications of the ITU-T G.712 recommendation. The CODEC includes
two complete μ-Law and A-Law companders. The μ-Law and A-Law companders are designed to
comply with the specifications of the ITU-T G.711 recommendation.
The block diagram in section 3 shows the main components of the W682510/W682310. The chip
consists of a PCM interface, which can process the data in parallel or serial formats. The PLL of the
chip provides the internal clock signals and synchronizes the CODEC sample rate with the external
frame sync frequency. The power-conditioning block provides the internal power supply for the digital
and the analog section, while the voltage reference block provides a precision analog ground voltage
for the analog signal processing.
8
DATA
R1
8 bit μ/A-Law
DAC
DATA
R2
μ/A-
Control
8
8 bit μ/A-Law
DAC
μ/A-
Control
8
DATA
T1
8 bit μ/A-Law
ADC
μ/A-
Control
8
DATA
T12
8 bit μ/A-Law
ADC
μ/A-
Control
f_C = 3400 Hz
Smoothing
Filter 1a
Smoothing
Filter 1b
f_C = 3400 Hz
Smoothing
Filter 2a
Smoothing
Filter 2b
f_C = 200 Hz
High Pass
Filter
f_C = 3400 Hz
Anti-Aliasing
Filter 1a
Anti-Aliasing
Filter 1b
f_C = 200 Hz
High Pass
Filter
f_C = 3400 Hz
Anti-Aliasing
Filter 2a
Anti-Aliasing
Filter 2b
-
+ _Buffer1
Av=1
-
+ _Buffer2
Av=1
-
+
-
+
FIGURE 7.1: THE W682510 AND W682310 SIGNAL PATH
RO1
RO2
AO1 -
AI1
AO2 -
AI2
7.1. TRANSMIT PATH
The A-to-D path of the CODEC contains an analog input amplifier with externally configurable gain
setting (see application examples in section 11). The transmit amplifier output is the input to the
encoder section.
The output of the input amplifier is fed through a low-pass filter to prevent aliasing at the switched
capacitor 3.4 kHz low pass filter. The 3.4 kHz switched capacitor low pass filter prevents aliasing of
input signals above 4 kHz, due to the sampling at 8 kHz. The output of the 3.4 kHz low pass filter is
filtered by a high pass filter with a 200 Hz cut-off frequency. The filters are designed according to the
recommendations in the G.712 ITU-T specification. From the output of the high pass filter the signal is
digitized. The signal is converted into a compressed 8-bit digital representation with either μ-Law or A-
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