HA12226F Datasheet, PDF (12/84 Pages) Hitachi Semiconductor – Audio Signal Processor for Cassette Deck(Dolby B-type NR with Recording System)

HA12226F/HA12227F
The Sensitivity Adjustment of Music Sensor
Adjusting MS Amp gain by external resistor, the sensitivity of music sensor can set up.
REP
V_CC
D V_CC
PB (L)
−6dB
C16 _R13
1000p _330k
+ _C13
0.33µ
8.2k
LPF
25kHz
MAI
MA MSIN MS
R_L
100k
OUT
DET
−
+
MS AMP
DET
50k
MS OUT
GND
Microcomputer
GND
PB (R)
Figure 4 Music Sensor Block Diagram
The Sensitivity of Music Sensor
A standard level of MS input pin 25.9 mVrms, therefore, the sensitivity of music sensor (S) can request it, by lower
formulas.
A = MS Amp Gain*¹
B = PB input Gain × (1/2)*²
C = Sensed voltage
S = 20log
C
[dB]
25.9 ⋅ A ⋅ B
20log (A × B) = D [dB]
S = 14 − D [dB]
C = 130 [mVrms] (Intenally voltage in a standard)
PB input Gain = 21.3 [dB]
Notes: 1. When there is not a regulation outside.
2. Case of one-sided channel input.
But necessary to consider the same attenuation quantity practically, on account of A(B) have made frequency
response.
G_V
37.7dB
f1
=
2π
⋅
1
C16
⋅
50k
[Hz]
f2 = 25k [Hz]
f
f1
f2
Figure 5 Frequency Characteristic of MSIN
Occasion of the external component of figure 4, f1 is 3.18 kHz.
Rev.6.00 Jun 15, 2005 page 12 of 83