CS42438 datasheet(32/62 Pages) CIRRUS

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DS646F1

CS42438

5.3.3

Digital Volume Control

5.3.3.1

Hardware Mode

DAC Volume Control and Mute are not accessible in Hardware Mode.

5.3.3.2

Software Mode

Each DAC’s output level is controlled via the Volume Control registers operating over the range of 0 to

-127.5 dB attenuation with 0.5 dB resolution. See “AOUTX Volume Control (Addresses 08h- 0Fh)” on

page 47. Volume control changes are programmable to ramp in increments of 0.125 dB at the rate con-

trolled by the SZC[1:0] bits in the Digital Volume Control register. See “Transition Control (Address 06h)”

on page 46.

Each output can be independently muted via mute control bits in the register “DAC Channel Mute (Ad-

dress 07h)” on page 47. When enabled, each AOUTx_MUTE bit attenuates the corresponding DAC to its

maximum value (-127.5 dB). When the AOUTx_MUTE bit is disabled, the corresponding DAC returns to

the attenuation level set in the Volume Control register. The attenuation is ramped up and down at the

rate specified by the SZC[1:0] bits.

5.3.4

De-Emphasis Filter

The CS42438 includes on-chip digital de-emphasis optimized for a sample rate of 44.1 kHz. The filter re-

sponse is shown in Figure 13. The de-emphasis feature is included to accommodate audio recordings

that utilize 50/15

µs pre-emphasis equalization as a means of noise reduction.

De-emphasis is only available in Single-Speed Mode. Please see

“DAC De-Emphasis Control

(DAC_DEM)” on page 44 for de-emphasis control.

AOUTx+

AOUTx-

Full-Scale Differential Output Level =

(AOUTx+) - (AOUTx-) = 6.5 VPP = 2.3 VRMS

4.125 V

2.5 V

0.875 V

5.0 V

4.125 V

2.5 V

0.875 V

Figure 12. Full-Scale Output

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