CS4270_06 Datasheet, PDF (30/49 Pages) Cirrus Logic – 24-Bit, 192 kHz Stereo Audio CODEC

CS4270
Analog
Input
2 kΩ
10 µF
AINx
2 kΩ
220 pF
CS4270
Figure 18. CS4270 Example Analog Input Network
5.4.2 Output Connections
The analog output filter present in the CS4270 is a switched-capacitor filter followed by a continuous time
low pass filter. Its response, combined with that of the digital interpolator, is given in Figures 24 - 47. The
recommended external analog circuitry is shown in Figure 19.
3.3µF
AOUTx
+
10kΩ
470Ω
Analog Output
C
Rext
CS4270
Rext _{+ 470}
C = _{4πFs ( Rext 470 )} For best 20 kHz response
Figure 19. CS4270 Recommended Analog Output Filter
5.5 Mute Control
The Mute Control pins become active during power-up initialization, reset, muting, when the MCLK to
LRCK ratio is incorrect, and during power-down. The MUTE pins are intended to be used as control for
an external mute circuit in order to add off-chip mute capability.
The CS4270 also features Auto-Mute, which is enabled by default. The Auto-Mute function causes the
MUTE pin corresponding to an individual channel to activate following the reception of 8192 consecutive
static-level audio samples on the respective channel. A single transition of data on the channel will cause
the corresponding MUTE pin to deactivate.
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 channel noise/signal-to-noise ratios which are only limited by the external mute
circuit. The MUTE pins are active-low. See Figure 20 for a suggested active-low mute circuit.
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