HA12203NT Datasheet, PDF (13/97 Pages) Hitachi Semiconductor – Audio Signal Processor for Cassette Deck(Dolby B-type NR with Recording System)

HA12203NT/HA12204NT
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
B = PB input Gain × (1/2)*¹
C = Sensed voltage
20log (A × B) = D [dB]
C = 130 [mVrms]
PB input Gain = 21.3 [dB]
S = 20log
C
[dB]
25.9 • A • B
S = 14 D [dB]
Notes: 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 C16.
But, with Attack *² and Recovery *³ the detection time differs exceptionally.
Recovery
Attack
Recovery
Attack
Recovery
Attack
C16
Function Characteristic of MS (1)
R18
Detection level
Input level
Function Characteristic of MS (2) Function Characteristic of MS (3)
Figure 6 Function Characteristic of MS
Like the figure 6(2), Recovery time is variably possible by value of resister R18. 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.
Notes 2. Attack : Non- music to Music
3. Recovery : Music to Non-music
• Music Sensor Output (MSOUT)
As for internal circuit of music sensor block, music sensor out pin is connected to the collector of NPN
type directly, output level will be “high” when sensing no signal. And output level will be “low”
when sensing signal.
Connection with microcomputer, it is requested to use external pull up resistor (R_L = 10 k• to 22 k•)
Note: Supply voltage of MSOUT pin must be less than V_CC voltage.
The Tolerances of External Components
For Dolby NR precision securing, please use external components shown at figure 7. If leak-current are a
few electrolytic-capacitor, it can be applicable to C5 and C23.
Note: As Dolby-NR aren't built-in at HA12204NT, R3, C5 and C23 aren't necessary.
Rev.3, Jun. 1999, page 13 of 97