Cirrus Logic CS4364 - Manual (Page 27)

DS619F1 27
CS4364
4.11 The MUTEC Outputs
The MUTEC1 pins have an auto-polarity detect feature. The MUTEC output pins are high impedance at the
time of reset. The external mute circuitry needs to be self biased into an active state in order to be muted
during reset. Upon release of reset, the CS4364 will detect the status of the MUTEC pins (high or low) and
will then select that state as the polarity to drive when the mutes become active. The external-bias voltage
level that the MUTEC pins see at the time of release of reset must meet the “MUTEC auto detect input
high/low voltage” specs as outlined in the Digital Characteristics section.
Figure 21 shows a single example of both an active high and an active low mute drive circuit. In these de-
signs, the pull-up and pull-down resistors have been especially chosen to meet the input high/low threshold
when used with the MMUN2111 and MMUN2211 internal bias resistances of 10 k
Ω.
Use of the Mute Control function is not mandatory but recommended for designs requiring the absolute min-
imum 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.
AOUT
Full-Scale Output Level= AOUT= 3.35 Vpp
4.175 V
2.5 V
0.825 V
Figure 19. Full-Scale Output
Figure 20. Recommended Output Filter