TEA0675T PHILIPS [NXP Semiconductors], TEA0675T Datasheet - Page 8

• Manufacturer Part Number: TEA0675T
• Description: Dual Dolby* B-type noise reduction circuit for playback applications
• Manufacturer: PHILIPS [NXP Semiconductors]

Philips Semiconductors
Notes
1. In AMS off mode, pin AMSEQ is HIGH level, the equalization time constant will be switched by pulling approximately
2. The high speed of the tape (FF, REW) at the tape head during AMS mode causes a transformation of level and
3. To activate the inputs IN1, pin HS might be left open-circuit. In this event the DC level at pin HS is 0.775V
1996 Jun 07
A
EQ switch input (not AMS mode)
I
I
I
H
V
I
V
V
EQ70
EQ120
EQth
HSW
SYMBOL
P/M
HSW
HSW(HIGH)
HSW(LOW)
EAD SWITCHING
Dual Dolby* B-type noise reduction circuit
for playback applications
200 A out of pin AMSEQ. This means for the device connected to pin AMSEQ, a restriction of input current at HIGH
level less than 200 A during AMS off; otherwise the selection of the equalization time constant is disabled and fixed
at 120 s. If the connected devices consume more than 200 A, this input has to be disconnected in AMS off mode.
(To ensure switching, the currents for the different switched modes are specified with a tolerance of 50 A in
Chapter “Characteristics”.) For an application with a fixed EQ time constant of 120 s the equalizing network may be
applied completely external. Change 8.2 k resistor to 14 k the internal resistor R
fixing the EQ switch input at the 70 s position (I
frequency of the originally recorded signal. It means a boost of signal level of approximately 10 dB and more for
recorded frequencies from 500 Hz up to 4 kHz. So the threshold level of 22 dB corresponds to signal levels in Play
Back (PB) mode of approximately 32 dB. The AMS inputs for each channel are pin SCA and pin SCB. As the
frequency spectrum is transformed by a factor of approximately 10 to 30 due to the higher tape speed in FF, REW,
the high-pass filter (4.7 nF/24 k ) removes the effect of offset voltages but does not affect the music search function.
In the application circuit (Fig.1) the frequency response of the system between tape heads input, e.g. pins INA2 and
INB2, to the AMS input pins SCA and SCB is constant over the whole frequency range (see Fig.3).
signal level at output for
AMS switching
pause to music
input current
input voltage
threshold current
pin voltage
input current
HIGH level pin voltage
LOW level pin voltage
PARAMETER
AMS mode; f = 10 kHz;
time constant 70 s active
time constant 120 s active
note 1
load current +90 to 90 A
V
inputs INA1 and INB1
active; note 3
inputs INA2 and INB2
active
HSW
= 0 to V
CONDITIONS
EQ70
CC
).
8
1
0
24
150
1000
170
2
V
CC
MIN.
+ 0.5
EQ
0.8V
21
200
TYP.
= 5.8 k is short-circuited by
CC
Preliminary specification
+170
V
1
18
250
2
CC
V
TEA0675
MAX.
CC
0.5
CC
.
UNIT
dB
V
V
V
A
A
A
A