TEA0679 NXP Semiconductors, TEA0679 Datasheet - Page 12

• Manufacturer Part Number: TEA0679
• Description: I2c-bus Controlled dual Dolby* B-type Noise Reduction Circuit for Playback Applications
• Manufacturer: NXP Semiconductors

Philips Semiconductors
Description of the principle timing diagram for AMS
scan mode without initial input signal (see Fig.5)
By activating the AMS scan mode the AMS output level
directly indicates whether the input level corresponds to a
pause level (V
At t
V
output changes to a LOW level: due to no signal at V
voltage at the level detector input V
below the level threshold and the second time constant will
be discharged (time detector input V
the time threshold level, the time detector output changes
to LOW level. Now the initial procedure is completed.
If a signal burst appears at t
voltage rises immediately and causes its output to charge
the second time constant, which supplies the input voltage
V
1998 Nov 12
handbook, full pagewidth
in
t
I
reduction circuit for playback applications
for the time detector.
, the following initial procedure runs until the AMS
0
t
2
r
= rise time; t
C-bus controlled dual Dolby* B-type noise
the AMS scan mode is activated. Without a signal at
to microprocessor
upper threshold
level threshold
time threshold
output signal
(hysteresis)
V AMSEQ
d
AMSEQ
4.5 V
= delay time; t
V ref
V in
V t
V l
AMS on
= LOW) or not (V
t 0
b
= burst time; t
3
, the level detector input
t 3 t 4
Fig.5 AMS scan mode without initial input signal.
t r
I
(CONTRA) remains
t
). When V
p
AMSEQ
= pause time; t
t 5 t 6
= HIGH).
t
t f
exceeds
t d
f
= fall time.
in
t 7
the
12
t 8 t 9 t 10
When V
time t
burst ends at t
level. Discharging of the second time constant begins
when the level threshold is exceeded at t
measures the delay time t
resistor and defines the length of a pause to be detected.
If no signal appears at V
time detector output switches the AMS output to a LOW
level at t
If a plop noise pulse appears at V
less than the rise time t
detected as music. The AMS output remains LOW.
Similarly the system handles no music pulses t
music appears at t
interruption will not affect the AMS output for t
t b
t r
r
(at t
t
7
exceeds the upper threshold level after the rise
.
4
) the AMS output changes to HIGH. If the signal
t 11 t 12
5
the level detector input V
11
with a small interruption at t
t 13 t 14
r
in
> t
t p
d
within the time interval t
, which is externally fixed by a
b
, the plop noise will not be
t d
t 15
in
V l : voltage at
pin 8 (CONTRA)
V t : voltage at
pin 25 (CONTRB)
(t
Product specification
8
level detector
input
time detector
input
) with a pulse width
TEA0679T
6
I
. The circuit then
falls to its LOW
MHB120
p
p
< t
: when
t
t
t
t
13
d
d
, this
.
, the