Datasheet

TLV320AIC1110
SLAS359 – DECEMBER 2001
2
www.ti.com
DESCRIPTION (Continued)
The PCM codec is an analog-digital interface for voice band signals designed with a combination of coders and
decoders (codecs) and filters. It is a low-power device with companding options and programming features, and
it meets the requirements for communication systems, including the cellular phone. The device operates in
either the 15-bit linear or 8-bit companded (µ-law or A-Law) mode, which is selectable through the I
2
C interface.
A coder, an analog-to-digital converter or ADC, digitizes the analog voice signal, and a decoder, a
digital-to-analog converter or DAC, converts the digital-voice signal to an analog output. The PCM codec
provides a companding option to overcome the bandwidth limitations of telephone networks without degrading
the sound quality. The human auditory system is a logarithmic system in which high amplitude signals require
less resolution than low amplitude signals. Therefore, an 8-bit code word with nonuniform quantization (µ-law
or A-law) has the same quality as 13-bit linear coding. The PCM codec provides better digital code words by
generating a 15-bit linear coding option.
The human voice is effective from a frequency range of 300 Hz to 3300 Hz in telephony applications. In order
to eliminate unwanted signals, the PCM codec design has two types of filters that operate in both the transmit
and receive path. A low-pass filter attenuates the signals over 4 kHz. A selectable high-pass filter cleans up the
signals under 100 Hz. This reduces noise that may have coupled in from 50/60-Hz power cables. The high-pass
filter is bypassed by selecting the corresponding register bit.
The PCM codec has many programming features that are controlled using a 2-wire standard serial I
2
C interface.
This allows the device to interface with many digital ICs such as a DSP or a microprocessor. The device has
seven registers: power control, mode control, transmit PGA, receive PGA, high DTMF, low DTMF, and auxiliary
mode control. Some of the programmable features that can be controlled by I
2
C interface include:
 Transmit amplifier gain
 Receive amplifier gain
 Sidetone gain
 Volume control
 Earphone control
 PLL power control
 Microphone selection
 Transmit channel high-pass filter control
 Receive channel high-pass filter control
 Companding options and selection control
 PCM loopback
 DTMF control
 Pulse density modulated control
The PCM codec is also capable of generating its own internal clocks from a 2.048-MHz master clock input.