SLAS763C August 2012 – October 2018 PCM5121 , PCM5122
PRODUCTION DATA.
An external digital host controls the PCM512x soft mute function by driving the XSMT pin with a specific minimum rise time (tr) and fall time (tf) for soft mute and soft un-mute. The PCM512x requires tr and tf times of less than 20 ns. In the majority of applications, this is no problem; however, traces with high capacitance may have issues.
When the XSMT pin is shifted from high to low (3.3 V to 0 V), a soft digital attenuation ramp begins. –1-dB attenuation is then applied every sample time from 0 dBFS to –∞. The soft attenuation ramp takes 104 samples.
When the XSMT pin is shifted from low to high (0 V to 3.3 V), a soft digital un-mute is started. 1-dB gain steps are applied every sample time from –∞ to 0 dBFS. The un-mute takes 104 samples.
In systems where XSMT is not required, it can be directly connected to AVDD.