TLC320AD80 Datasheet, PDF (12/37 Pages) Texas Instruments – Audio Processor Subsystem

2 Functional Description
The TLC320AD80 is an audio processing subsystem that includes a high-performance stereo audio DAC,
analog volume and balance control, analog TV monaural decoder, de-emphasis filter, and an analog
wide-band multiplexer. The sigma-delta DAC performs data conversion with 85-dB performance. The
architecture provides much flexibility with the option to use all or some of the functional blocks.
The digital interfaces enable ease of use by providing compatibility with the industry standard I²S digital
audio port, and with the SPI serial control interface. The digital audio serial interface also supports additional
interface protocols and 16-bit or 18-bit data formats.
The analog interface provides much flexibility. Four analog audio sources are supported including two stereo
audio sources, a TV baseband audio signal, and one mono source. In addition, the inputs to the volume and
balance and the wideband mux are external to the chip. This allows the option to connect intermediate
analog functions between functional blocks. As a default, these connections should include dc blocking
capacitors to eliminate analog offsets. Finally, the primary analog output of the device is provided by a
multiplexer. This allows selection from one of the following sources: the DAC, the output of the monaural
decoder, or pass-through of one of the analog inputs. The multiplexer also allows the two stereo inputs to
be used as mono inputs. In this case, the left channel is routed into both the left and right outputs.
The TLC320AD80 integrates several audio functions into one device. Following is a brief description of the
device. Subsections of this chapter describe the details. The functions include:
• Sigma-delta stereo DAC
• 50/15 ms de-emphasis analog filter
• Analog volume and analog balance control
• Output multiplexer to select between the various audio sources
• TV baseband monaural audio decoder
• Additional uncommitted 2:1 mono multiplexer
• Two flexible digital audio input ports
• A SPI compatible serial control interface
• Voltage reference with buffered output
The DAC audio input can be selected from either of the digital serial ports. Several sample rates are
supported. In addition, a software-selectable 50/15 µs de-emphasis filter is provided in the analog section
of the DAC. The output of the DAC is fed into the output multiplexer. The aforementioned serial ports provide
several timing protocols (Phillips I²S, left justified, right justified, DSP mode), each with 16-bit or 18-bit data
formats.
The TV baseband monaural decoder receives differential audio inputs from two external terminals (TV
BASEBAND P, TV BASEBAND M). The output of this decoder is fed into the output multiplexer. The decoder
is a differential eighth order elliptic switched capacitor filter used to reject high frequency audio signals that
may be present in the NTSC audio broadcast multiplex. Proper operation of this section requires that the
master clock (MCLK) correspond to an audio sample rate of 32 kHz.
The analog volume and balance control receives inputs from external terminals. The output of this section
provides independent stereo and mono outputs on three terminals. All three outputs are also short-circuit
protected. The functionality of this block provides either ganged or individual gain control for the left and the
right channel. There are 69 volume settings which range from 6 dB to –62 dB of gain in 1 dB/step increments.
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