CS4265 Datasheet, PDF (27/53 Pages) Cirrus Logic – 105 dB, 24-Bit, 192 kHz Stereo Audio CODEC

CS4265
channel noise/signal-to-noise ratios which are only limited by the external mute circuit. The MUTEC pin is an active-
low CMOS driver. See Figure 14 below for a suggested active-low mute circuit.
+V_EE
AOUT
LPF
AC
Couple
560 Ω
A udio
O ut
47 kΩ
-V _{E E}
CS4265
MUTE C
+V_A
MMU N 2111LT 1
2 kΩ
10 kΩ
-V _{E E}
Figure 14. Suggested Active-Low Mute Circuit
4.12 AES3 Transmitter
The CS4265 includes an IEC60958-3 digital audio transmitter. A comprehensive buffering scheme provides write
access to the channel status data. This buffering scheme is described in “Channel Status Buffer Management” on
page 50.
The IEC60958-3 transmitter encodes and transmits audio and digital data according to the IEC60958-3 (S/PDIF)
interface standard. Audio and control data are multiplexed together and bi-phase mark encoded. The resulting bit
stream is driven to an output connector either directly or through a transformer. The transmitter is clocked from the
clock input pin MCLK.
The channel status (C) bits in the transmitted data stream are taken from storage areas within the CS4265. The user
can manually access the internal storage of the CS4265 to configure the transmitted channel status data. The sec-
tion “Channel Status Buffer Management” on page 50 describes the method of manually accessing the storage ar-
eas. The CS4265 transmits all ‘0’s in the user (U) data fields.
4.12.1 TxOut Driver
The line driver is a low skew, low impedance, single-ended output capable of driving cables directly. The driver is
set to ground during reset (RESET = LOW), when no transmit clock is provided, and optionally under the control of
a register bit. The CS4265 also allows immediate muting of the IEC60958-3 transmitter audio data through a control
register bit.
External components are used to terminate and isolate the external cable from the CS4265. These components are
detailed in “External IEC60958-3 Transmitter Components” on page 49.
4.12.2 Mono Mode Operation
An IEC60958-3 stream may be used in more than one way to transmit 192 kHz sample rate data. One method is to
double the frame rate of the current format. This results is a stereo signal with a sample rate of 192 kHz. An alternate
method is implemented using the two sub-frames in a 96 kHz frame rate IEC60958-3 signal to carry consecutive
samples of a mono signal, resulting in a 192 kHz sample rate stream. This allows older equipment, whose
IEC60958-3 transmitters and receivers are not rated for 192 kHz frame rate operation, to handle 192 kHz sample
DS657A2
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