CS4265 Datasheet, PDF (26/53 Pages) Cirrus Logic – 105 dB, 24-Bit, 192 kHz Stereo Audio CODEC

CS4265
4.8 DAC Serial Data Input Multiplexer
The CS4265 contains a 2-to-1 serial data input multiplexer. This allows two separate data sources to be input into
the DAC without the use of any external multiplexing components. The “DAC SDIN Source (Bit 7)” section on
page 36 describes the control port settings necessary to control the multiplexer.
4.9 De-Emphasis Filter
The CS4265 includes on-chip digital de-emphasis optimized for a sample rate of 44.1 kHz. The filter response is
shown in Figure 13. The frequency response of the de-emphasis curve will scale proportionally with changes in sam-
ple rate, Fs. Please see section 6.3.3 for de-emphasis control.
The de-emphasis feature is included to accommodate audio recordings that utilize 50/15 µs pre-emphasis equaliza-
tion as a means of noise reduction.
De-emphasis is only available in Single Speed Mode.
Gain
dB
0dB
T1=50 µs
-10dB
T2 = 15 µs
F1
3.183 kHz
F2 Frequency
10.61 kHz
Figure 13. De-Emphasis Curve
4.10 Internal Digital Loopback
The CS4265 supports an internal digital loopback mode in which the output of the ADC is routed to the input of the
DAC. This mode may be activated by setting the LOOP bit in the Signal Selection register (06h - See page 36).
When this bit is set, the status of the DAC_DIF[1:0] bits in register 03h will be disregarded by the CS4265. Any
changes made to the DAC_DIF[1:0] bits while the LOOP bit is set will have no impact on operation until the LOOP
bit is cleared, at which time the Digital Interface Format of the DAC will operate according to the format selected by
the DAC_DIF[1:0] bits. While the LOOP bit is set, data will be present on the SDOUT pin in the format selected by
the ADC_DIF bit in register 04h.
4.11 Mute Control
The MUTEC pin becomes active during power-up initialization, reset, muting, if the MCLK to LRCK ratio is incorrect,
and during power-down. The MUTEC pin is intended to be used as control for an external mute circuit in order to
add off-chip mute capability.
Use of the Mute Control function is not mandatory but recommended for designs requiring the absolute minimum in
extraneous clicks and pops. Also, use of the Mute Control function can enable the system designer to achieve idle
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