HA12179F Datasheet, PDF (12/40 Pages) Hitachi Semiconductor – Audio Signal Processer for Car Deck and Cassette Deck(Dolby B-type NR with PB Amp)

HA12179F
Input Block Diagram and Level Diagram
R34
5.1k _R35
5.1k
EQ OUT
C24
0.1µ
TAI
R38
330k
R39
180
R36
30mVrms
12k _{EQ OUT-M (–28.2dBs)}
R37
18k
EQ AMP.
C25
0.01µ NFI
–+
RIN
VREF
0.6mVrms
(–62.2dBs)
FIN
HA12179F : 387.5mVrms (–6.0dBs)
PBOUT
INPUT AMP
+
–
NR circuit
RECOUT
300mVrms
(–8.2dBs)
Note: The each level shown above is typical value when offering PBOUT level to PBOUT pin. (EQ AMP.)
Gv = 40 dB, f = 1 kHz
Figure 3 Input Block Diagram
Adjustment of Playback Dolby Level
After replace R34 and R35 with a half-fix volume of 10 kΩ, adjust RECOUT level to be Dolby level with
playback mode.
Note on Connecting with Tape Head to IC
This IC has no internal resistor to give the DC bias current to equalizer amp., therefore the DC bias current
will give through the head. This IC provides the Vref buffer output pin for Rch and Lch separately (has
two Vref terminal). In case of use that the Rch and Lch reference of head are connected commonly, please
use one of Vref terminals of IC (47 pin or 52 pin) for head reference.
If both 47 pin and 52 pin of IC are connected, rush current give the great damage to IC. The application
circuit is shown in figure 4.
Rev.1, Apr. 1994, page 12 of 40