Rohm BU7858KN, Техническая заметка

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【 BU7893GU 】
Fig.29 AUDIO I/F Format (BU7893GU)
●
3D SURROUND ENHANCEMENT FUNCTION
【 BU7893GU 】
Even under the circumstances of adjacent arrangement of stereo speakers, the wide-spreading acoustic effect can be
achieved because of the output resulting from the digital audio input to which the 3D surround effect has been applied.
Moreover, the stereo sound at the time of audio recording can also be played truly. Please tell us about the parameter
setting when you use this function.
●
LOW-BAND CORRECTIVE CIRCUIT
In the headphone output terminals (HP_L, HP_R or HPOL, HPOR), there is a low-band corrective circuit, which corrects
the low-band attenuation.
Fig.30 BU7858KN & BU7893GU Headphone Output Equivalent Circuit
Low-band cut-off frequency fC= 1/(2
･π･
CL
･
RL)
Low-band boost frequency fBOOST = 1/(2 ･π･ CCHPx ･ 200k Ω )
Boost gain ABOOST = 20
･
log((200 k
Ω
+1/(2
･π･
f
･
CCHPx))/100 k
Ω
)
（ the maximum low-band boost is 6dB ）
For parameter setting, determine the output coupling capacitance CL and the headphone impedance R
L
before calculating
the low-band cut-off frequency fC. Then determine CCHPx so that the low-band cut-off frequency fC is roughly in agreement
with the low-band boost frequency fBOOST.
The recommended parameter setting of BU7858KN and BU7893GU is CCHPx = 6800pF at the time of CL = 100
μ
F and RL
= 16 Ω .
+
-
200k
Ω
200k Ω
+
HP_X
or
HPOX
CA_X
or
CCX
C
CHPx
C
L
R
L
OUTPUT
100k
Ω
0 1 2 3 13 14 15 16 17 18 29 30 31 1 2 3 13 14 15 16 17 18
29 30 31
0
0
Rch Lch
BCLK
LRCLK
1. MSBファースト前詰フォーマット
Don't
care
15 14 13 2 1 0 15 14 13 2 1 0
Don't
care
Don't
care
Don't
care
15
SDI
3. IIS
フォーマット
Don't
care
Don't
care
Don't
care
Don't
care
SDI
2. MSBファースト後詰フォーマット
0 1 2 3 4 14 15 16 17 18 19 30 31 1 2 3 14 15 16 17 18 19 30 31 0 0
Rch Lch
BCLK
LRCLK
Don't
care
15 14 13 2 1 0
Don't
care
Don't
care
Don't
care
15 14 13 2 1 0
Don't
care
SDI
4
15 14 13 2 1 0 2 1 0 15 14 13
MSB first right justified format
IIS format
MSB first left justified format