HA12209F Datasheet, PDF (11/49 Pages) Hitachi Semiconductor – Audio Signal Processor for Cassette Deck(Dolby B-type NR with Recording System)

The sensitivity of Music Sensor
Gv
HA12209F
f1 =
1
[Hz]
2π · C26 · 100k
f2 = 25k [Hz]
f
f1
f2
Figure 5 Frequency Characteristic of MSIN
Occasion of the external component of figure 4, f1 is 159Hz. A standard level of MS input pin
25.9mVrms, therefore, the sensitivity of music sensor (S) can request it, by lower formulas.
A = MS Amp Gain
B = PB input Gain × (1/2)*¹
C = Sensed voltage
S = 20log
C
[dB]
25.9 · A · B
20log (A × B) = D [dB]
PB input Gain = 21.3 [dB]
S = 14 – D [dB]
Note: 1. Case of one-sided channel input.
Time Constant of Detection
Figure 6(1) generally shows that detection time is in proportion to value of capacitor C10. But, with
Attack*² and Recovery*³ the detection time differs exceptionally.
Recovery
Attack
Recovery
Attack
Recovery
Attack
C10
Function Characteristic of MS (1)
R12
Detection level
Input level
Function Characteristic of MS (2) Function Characteristic of MS (3)
Figure 6 Function Characteristics of MS
Like the figure 6(2), Recovery time is variably possible by value of resistor R12. 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.
Note: 2. Attack : Non-music → Music
3. Recovery : Music → Non-music
Rev.2, Jun. 1999, page 11 of 49