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Digital De-Emphasis

SOFTWARE MODE CONFIGURATION

Digital Attenuation

Digital De-Emphasis

Soft Mute

Zero Data Mute

PCM4104-EP

SBAS419 – JUNE 2007

This is a global digital function (common to all four channels) and provides de-emphasis of the higher frequency

content within the 20-kHz audio band. De-emphasis is required when the input audio data has been

pre-emphasized. Pre-emphasis entails increasing the amplitude of the higher frequency components in the

20-kHz audio band using a standardized filter function in order to enhance the high-frequency response. The

PCM4104 de-emphasis filters implement the standard 50/15

μs de-emphasis transfer function commonly used in

digital audio applications.

De-emphasis filtering is available for three input sampling frequencies in Single Rate sampling mode: 32 kHz,

44.1 kHz, and 48 kHz. De-emphasis is not available when operating in Dual or Quad Rate sampling modes. The

de-emphasis filter is selected using the DEM0 (pin 12) and DEM1 (pin 11) inputs. Table 5 illustrates the

de-emphasis filter configuration for Standalone mode.

Table 5. Digital De-Emphasis Configuration

DEM1

DEM0

DIGITAL DE-EMPHASIS MODE

0

0

Off (de-emphasis disabled)

0

1

48 kHz

1

0

44.1 kHz

1

1

32 kHz

Software mode is selected by forcing the MODE input(pin 8) high. Software mode operation provides full access

to the features of the PCM4104 by allowing the writing and reading of on-chip control registers. This is

accomplished using the four-wire SPI port. The following paragraphs provide a brief description of each function

available when using Software mode.

The audio signal for each channel can be attenuated in the digital domain using this function. Attenuation

settings from 0 dB (unity gain) to –119.5 dB are provided in 0.5 dB steps. In addition, the attenuation level may

be set to the mute state. The rate of change for the digital attenuation function is one 0.5 dB step for every eight

LRCK periods. Each channel has its own independent attenuation control, accessed using control registers 1

through 4. The reset default setting for all channels is 0 dB, or unity gain (no attenuation applied).

The de-emphasis function is accessed through Control Register 5 using the DEM[1:0] bits. The reset default

setting is that the de-emphasis is disabled for all four channels. De-emphasis filter operation is described in the

Standalone Mode Configuration section of this data sheet.

Each of the four D/A converter channels has its own independent soft mute control, located in Control Register

5.

The reset default is normal output for all four channels with the soft mute function disabled. The MUTE input (pin

10) also functions in Software mode, with a high input forcing soft mute on all four channels.

The PCM4104 includes a zero data detection and mute function in Software mode. This function automatically

mutes a given channel when 1024 consecutive LRCK periods of all zero data are detected for that channel. The

zero data mute function is enabled and disabled using the ZDM bit in Control Register 5. The zero data mute

function is disabled by default on power up or reset.

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