HA12179F Datasheet, PDF (15/40 Pages) Hitachi Semiconductor – Audio Signal Processer for Car Deck and Cassette Deck(Dolby B-type NR with PB Amp)

HA12179F
• Normal mode
Gv1
=
20
log
₁
+
R27
R28

[dB]
f1 =
1
[Hz], f2 = 25 k [Hz]
2 ⋅π ⋅C14 ⋅100 k
• FF or REW mode
Gv
2
=
20
log
₁
+
R25
R26

[dB]
f3 =
1
[Hz], f4 = 25k [Hz]
2 ⋅ π⋅ C28⋅R26
A standard level of TAI pin is 30 mVrms and the gain for TAI to MS AMP input is 10times, therefore, the
other channel sensitivity of music sensor (S) is computed by the formula mentioned below.
S
=
20
log


C
30
⋅
1
10 ⋅

A _
[
dB]
A = MS AMP. gain (B dB)
C = The sensing level of music sensor
S = –7.3 – B[dB] C = 130 mVrms (typ.)
S is 6 dB up in case of the both channels.
Music Sensor Time Constant
• Sensing no signal to signal (Attack) is determind by C13.
0.01 µF to 1 µF capacitor C13 can be applicable.
• Sensing signal to no signal (Recovery) is determind by C13 and R24, however preceding (Attack), 100
kΩ to 1 MΩ R24 can be applicable.
Music Sensor Output (MS OUT)
As for the internal circuit of music sensor block, music sensor out pin is connected to the collector of NPN
Type directly, therefore, output level will be “high” when sensing no signal. And output level will be
“low” when sensing signal.
Connection with microcomputer, design I_L at 1mA typ.
I_L
=
DV_CC
– MSOUT_Lo *
R_L
* MSOUT_LO: Sensing signal (about 1 V)
Notes: 1. Supply voltage of MS OUT pin must be less than V_CC voltage.
2. MS V_CC pin and V_CC pin are required the same voltage.
Rev.1, Apr. 1994, page 15 of 40