Datasheet

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3-D Sound
Three-Band Tone Control
Digital Monaural Mixing
Zero-Cross Detection
Short Protection
Pop-Noise Reduction Circuit
Power Up/Down for Each Module
Digital Audio Interface
Digital Interface
Power Supply
PCM1774
SLAS551 – JULY 2007
A 3-D sound effect is provided by mixing L-channel and R-channel data with a band-pass filter with two
parameters, mixing ratio and band pass filter characteristic, that can be controlled by register 95 (3DP[3:0],
3FLO).
Tone control has bass, midrange, and treble controls that can be adjusted from 12 dB to –12 dB in 1-dB steps
by registers 92 to 94 (LGA[4:0], MGA[4:0] and HGA[4:0]). Register 92 (LPAE) attenuates the digital input signal
automatically to prevent clipping of the output signal at settings above 0 dB for bass control. LPAE has no effect
on midrange and treble controls.
The audio data can be converted from stereo digital data to mixed monaural digital data. The conversion occurs
in the internal audio interface section and is controlled by register 96 (MXEN).
Zero-cross detection minimizes audible zipper noise while changing analog volume and digital attenuation. This
function applies to the digital input or digital output as defined by register 86 (ZCRS).
The short-circuit protection on each headphone output prevents damage to the device while an output is shorted
to V
PA
, an output is shorted to PGND, or any two outputs are shorted together. When the short circuit is detected
on the outputs, the PCM1774 powers down the shorted amplifier immediately. The short-protection status can
be monitored by reading register 77 (STHC, STHL, SCHR) through the I
2
C interface. Short-circuit protection
operates in any enabled headphone amplifier.
The pop-noise reduction circuit prevents audible noise when turning the power supply on/off and powering the
device up/down in portable applications. It is recommended to establish the register settings in the sequence
that is shown in Table 3 and Table 4 . No particular external parts are required.
Using register 72 (PMXL, PMXR), register 73 (PBIS, PDAR, PDAL, PHPR, PHPL) and register 90 (PCOM),
unused modules can be powered down to minimize power consumption (7 mW during playback only).
The PCM1774 can receive I
2
S, right-justified, left-justified, and DSP formats in both master and slave modes.
These options can be selected in register 70 (PFM[1:0]), register 81 (RFM[1:0]) and register 84 (MSTR).
All digital I/O pins can interface at various power supply voltages. V
IO
pin can be connected to a 1.71-V to 3.6-V
power supply.
The V
CC
pin and the V
PA
pin can be connected to 2.4 V to 3.6 V. The same voltage must be applied to both pins.
The V
DD
pin and the V
IO
pin can be connected to 1.71 V to 3.6 V. A different voltage can be applied to each of
these pins (for example, V
DD
= 1.8 V, V
IO
= 3.3 V).
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