W6811

Publication Release Date: September, 2005

- 8 -

Revision A12

7. FUNCTIONAL DESCRIPTION

W6811 is a single-rail, single channel PCM CODEC for voiceband applications. The CODEC complies

with the specifications of the ITU-T G.712 recommendation. The CODEC also includes a complete

μ-

Law and A-Law compander. 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 W6811. The chip consists of a

PCM interface, which can process long and short frame sync formats, as well as GCI and IDL formats.

The pre-scaler 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. The main CODEC block diagram is shown in

section 3.

Figure 7.1 The W6811 Signal Path

PAO+

PAO

8

μ/A-

Cont

AI+

AI -

w

μ/A-

Cont

o

AO

+

RO -

-

VA

G

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 device has an input operational amplifier whose

output is the input to the encoder section. If the input amplifier is not required for operation it can be

powered down and bypassed. In that case a single ended input signal can be applied to the AO pin or

the AI- pin. The AO pin becomes high input impedance when the input amplifier is powered down. The

(see Table 7.1).

Ant

Ant

-Aliasi

Filter

= 3400

Hz

i

-Aliasi

ng

Filter

Hz

High

Pas

Filt

Smooth

ngFilter

2

Hz

Filter

1

Smooth

ng

8

μ/A

Control

8

μ/A-

Control

+ -

- +

+

-

PAI

Ant

Ant

High Pass

-Aliasing

Filter

-

Aliasing

Filter

-

Filter

Filter

Smoothing

Filter

Filter

Filter

Filter

Smoothing

Receive Path

Transmit Path

D/A

Converter

+

-

-

A/D

Converter

C

= 200Hz

f