HA12215F Datasheet, PDF (12/69 Pages) Hitachi Semiconductor – Audio Signal Processor for Cassette Deck(Dolby B-type NR with Recording System)

HA12215F
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.
Time constant of detection
Figure 6(1) generally shows that detection time is in proportion to value of capacitor C13. But, with
Attack*² and Recovery*³ the detection time differs exceptionally.
Notes 2. Attack : Non- music to Music
3. Recovery : Music to Non-music
Recovery
Attack
Recovery
Attack
Recovery
Attack
C13
R13
Detection level _{Input level}
(1)
(2)
(3)
Figure 6 Function Characteristic of MS
Like the figure 6(2), Recovery time is variably possible by value of resistor R13. But Attack time gets
about fixed value. Attack time has dependence by input level. When a large signal is inputted, Attack time
is short tendency.
Rev.5, Oct. 1999, page 12 of 69