BU9408KS2_12 Datasheet, PDF (46/57 Pages) Rohm – 32bit Audio DSP with Built-in 4ch DAC and ASRC

BU9408KS2
Technical Note
6. 8x Over-Sampling Digital Filter (DF)
In each BU9408KS2 audio analog signal output DAC, an 8x over-sampling digital filter is inserted into the previous step of
the DAC input.
In addition to filter calculations, this block also performs pre-scaler, volume and Lch/Rch mix functions.
BU9408KS2’s DF+DAC configurations are as follows:
DF1
Pre-scaler
Volume
Chanel Mixer
X8 Oversampling
Digital filter
DF2
Pre-scaler
Volume
Chanel Mixer
X8 Oversampling
Digital filter
ΔΣDAC
AOUTL2
(22PIN)
AOUTR2
(20PIN)
16bit DAC
AOUTL1
(17PIN)
AOUTR1
(16PIN)
6-1. Pre-Scaler Function (Attenuation)
The signal levels are adjusted in order to bring out the audio DAC performance.
For DF1, refer to &h90[7:0] and &h91[7:0]. The default value is h4000.
For DF1, refer to &h93[7:0] and &h94[7:0]. The default value is h4000.
6-2. Volume Function
The volume value can be configured in 0.5dB increments from +6dB to -121dB.
To change the volume value, coefficient soft transition takes place.
The expression in the transition time from x[dB] to y[dB] is |(10^(x/20)-10^(y/20)|*21.4ms. The transition time is 21.4ms when
it is from 0dB to -∞. Recommend that this setting value is 0dB and under.
Default = FFh
Select Address
DF1 &h92 [ 7:0 ]
DF2 &h95 [ 7:0 ]
Operation Description
Calculation format: (12-command value) x 0.5dB
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2012.03 - Rev.A