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PDF TEA0675 Data sheet ( Hoja de datos )
| Número de pieza | TEA0675 | |
| Descripción | Dual Dolby* B-type noise reduction circuit for playback applications | |
| Fabricantes | NXP Semiconductors | |
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INTEGRATED CIRCUITS
DATA SHEET
TEA0675
Dual Dolby* B-type noise reduction
circuit for playback applications
Preliminary specification
Supersedes data of July 1993
File under Integrated Circuits, IC01
1996 Jun 07
1 page  
Philips Semiconductors
Dual Dolby* B-type noise reduction circuit
for playback applications
Preliminary specification
TEA0675
FUNCTIONAL DESCRIPTION
Noise Reduction (NR) is enabled when pin HPB is
open-circuit and disabled when connected to GND via an
1.5 kΩ resistor.
Dolby B noise reduction only operates correctly if 0 dB
Dolby level is adjusted at 387.5 mV.
Automatic Music Search (AMS) scan mode is enabled
when pin HPA is connected to VCC via an 1.5 kΩ resistor
and disabled when pin HPA is open-circuit. Switching AMS
on, internally NR is switched OFF simultaneously
(see Figs 5 and 6 for principle timing in AMS-scan mode).
AMS-latch mode is enabled when pin HPA is connected
to GND via an 1.5 kΩ resistor and disabled when pin HPA
is open-circuit. Switching AMS on, NR is switched off
internally. In this mode the device detects a pause level
signal, when a music level signal has appeared first
(see Figs 7 and 8 for principle timing). Furthermore a
longer rise time constant is supplied for suppressing the
detection of plops on tape. The output signal at pin
AMSEQ in this mode may be applied to drive a tape driver
logic circuit.
Equalization time constant switching (70 µs or 120 µs)
is achieved when pin AMSEQ is connected to GND via an
18 kΩ resistor (120 µs), or left open-circuit (70 µs).
This does not affect the AMS output signal during AMS
mode (see Fig.1).
Head switching is achieved when pin HS is connected
(input IN2 active) to GND via a 27 kΩ resistor, or left
open-circuit (input IN1 active). The 10 µF capacitor at pin
HS sets the time constants for smooth switching.
In AMS mode the signals of both channels are rectified and
then added. This means, even if one channel signal
appears inverted to the other channel, the normal AMS
function is ensured. Pins HPB and HPA perform the
function of a logic input for AMS, respectively NR mode
switching in both channels and provide the frequency
dependent feedback of the control chain amplifier in the
corresponding channel. Thus it is important that no voltage
is applied to pins HPB and HPA during NR on/AMS off
mode, otherwise this will cause irregular NR
characteristics.
LIMITING VALUES
In accordance with the Absolute Maximum Rating System (IEC 134).
SYMBOL
PARAMETER
VCC
Vi
tshort
Tstg
Tamb
Ves
supply voltage
input voltage (except pin 11)
pin 11 (Vref) to VCC short-circuiting duration
storage temperature
operating ambient temperature
electrostatic handling voltage for all pins
CONDITIONS MIN.
0
note 1
note 2
−0.3
−
−55
−40
−2
−500
Notes
1. Human body model (1.5 kΩ, 100 pF).
2. Machine model (0 Ω, 200 pF).
MAX.
14
+VCC
5
+150
+85
+2
+500
UNIT
V
V
s
°C
°C
kV
V
1996 Jun 07
5
5 Page 
Philips Semiconductors
Dual Dolby* B-type noise reduction circuit
for playback applications
Preliminary specification
TEA0675
Description of the principle timing diagram for AMS-scan mode without initial input signal (see Fig.5)
handbtro:orki,sfeulltipmaegewidth
AMS on
tr
tb<tr
td: delay time
td
tb: burst time
tp: pause time
tf: fall time
Vin
tf
tp<td
t
Vl
level threshold
VREF
Vt
upper threshold
(hysteresis)
time threshold
Vl: voltage at
level detector
input
pin 3 (CONTRA)
t
Vt: voltage at
time detector
input
pin 22 (CONTRB)
VAMSEQ
4.5 V
output signal
to microprocessor
t0
t3 t4
t5 t6
t7 t8 t9 t10
t11 t12 t13 t14
t15
Fig.5 AMS-scan mode without initial input signal.
t
t
MED625
By activating AMS-scan mode, the AMS output level
directly indicates whether the input level corresponds to a
pause level (VAMSEQ = LOW) or not (VAMSEQ = HIGH).
At t0 the AMS-scan mode is activated. Without a signal at
Vin, the following initial procedure runs until the AMS
output changes to LOW level: due to no signal at Vin the
voltage at the level detector input VI (pin 3, CONTRA)
remains below the level threshold and the second time
constant will be discharged (time detector input Vt).
When Vt passes the time threshold level, the time detector
output changes to LOW level. Now the initial procedure is
completed.
If a signal burst appears at t3, the level detector input
voltage rises immediately and causes its output to charge
the second time constant, which supplies the input voltage
Vt for the time detector. When Vt passes the upper
threshold level after the rise time tr (at t4), the AMS output
changes to HIGH. If the signal burst ends at t5 the level
detector input VI falls to its LOW level. When passing the
level threshold at t6, the discharging of the second time
constant begins. Now the circuit measures the delay time
td, which is externally fixed by a resistor and defines the
length of a pause to be detected. If no signal appears at Vin
within the time interval td, the time detector output switches
the AMS output to LOW level at t7.
If a plop noise pulse appears at Vin (t8) with a pulse width
less than the rise time tr > tb, the plop noise will not be
detected as music. The AMS output remains LOW.
Similarly the system handles ‘no music pulses’ tp: when
music appears at t11 with a small interruption at t13, this
interruption will not affect the AMS output for tp < td.
1996 Jun 07
11
11 Page | ||
| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet TEA0675.PDF ] | |
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