BU26154MUV_15 Datasheet, PDF (26/90 Pages) Rohm – Monaural Audio CODEC with Touch Panel Interface

BU26154MUV
Datasheet
Filter (5bands-Programmable IIR Filter)
A five bands equalizer features a second-order IIR type Band Pass Filter. Volume control of MUTE, -71.5dB to +12dB
(0.5dB step) can be controlled at all paths.
Each channels of the filter can be selected parallel connection or serial connection
The followings are block diagrams at parallel connection and serial connection
Input
Coefficient(a0, a1) X 5ch gain X 5ch
Band0-IIR
Coefficient(a0, a1) X 5ch
Input
Band0-IIR
Band1-IIR
Band2-IIR
Band3-IIR
Band4-IIR
gain X 5ch
Output
Band1-IIR
Band2-IIR
Band2-IIR
Band4-IIR
Output
Parallel connection
Figure 29
Serial connection
Figure 30
The filter coefficient is programmable. From required center frequency and band width, Programmable Equalizer
Coefficient-a0 Control Register and Programmable Notch Filter Coefficient-a1 Control Register value is decided. Followings
are the setting formula.
a0 = (1 - tanπf_b/fs) / (1 + tanπf_b/fs)
a1 = - 2cos2πf₀/fs / (1 + tanπf_b/fs)
f0: Band center frequency [Hz]
fb: -3dB band width [Hz]
fs: Sampling frequency [Hz]
* Actual setting value is an integral number that the result of above formula multiplied by 2¹⁴ then round up numbers of five
and above and round down anything under five to a integer.
DSP filtering function: ON / OFF
DSP Filter Function Enable register can set ON or OFF of each filter function. Please change this register when
RECPLAY bit is 0x0. If this register is changed on playback or recording, the noise may be generated.
ALC Auto Level Control
Please refer the application note “AutoLevelControlApplicationNote”.
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26.Oct.2015 Rev.002