4.4 CLASSD Attenuator
The CLASSD features a digital attenuator with an attenuation range of 0–77 dB and a step size of 1 dB. When attenuation greater than 77 dB is programmed, the attenuator mutes the channel. Attenuation can be done individually for both right and left channels.
The following table shows the allowed settings for input sample rates, DSPCLK and filter support for each available sample rate.
| Sample Rate (fs) | Filter Type / DSPCLK | Equalizer | De-emphasis Filter | Attenuator | |
|---|---|---|---|---|---|
| 12.288 MHz | 11.2896 MHz | ||||
| 8 kHz | 2 | - | Y | N | Y |
| 16 kHz | 2 | - | Y | N | Y |
| 32 kHz | 2 | - | Y | Y | Y |
| 48 kHz | 1 | - | Y | Y | Y |
| 96 kHz | 3 | - | Y | N | Y |
| 22.05 kHz | - | 1 | Y | N | Y |
| 44.1 kHz | - | 1 | Y | Y | Y |
| 88.2 kHz | - | 3 | Y | N | Y |
Note:
- The "Filter Type / DSPCLK" column in the above table without a numerical entry implies an unavailable CLASSD setting. Such configuration will raise the Configuration Error (CFGERR) flag.
- Y – DSP component supported.
- N – DSP component not supported.
- For the attenuator, a minimum attenuation of 1dB should be configured to avoid saturation in the PWM stage.