TEA0675T PHILIPS [NXP Semiconductors], TEA0675T Datasheet - Page 13

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

Philips Semiconductors
Description of the principle timing diagram for AMS-latch mode without initial input signal (see Fig.7)
This is similar to the description of the principle timing
diagram from AMS-scan mode. It only differs in its initial
behaviour and its rise time t
different t
for latch and scan mode).
Running in AMS-latch mode, the circuit may be simply
applied to drive a stop solenoid via a power FET. So the
AMS output signal has not to be processed by a controller.
Because there is no processor to make a decision whether
there is a plop noise or not, for this mode the rise time t
extended to approximately 150 ms.
By activating AMS-latch mode the AMS output will not
change to LOW level at t
1996 Jun 07
Dual Dolby* B-type noise reduction circuit
for playback applications
handbook, full pagewidth
r
does not occur in the principle timing diagrams
t r : rise time
t d : delay time
t b : burst time
t p : pause time
t f : fall time
upper threshold
level threshold
latch status
time threshold
to power FET
output signal
(hysteresis)
internal
V AMSEQ
V REF
4.5 V
V in
V l
V t
H
2
L
if there is no initial signal at V
AMS on
r
. (Please notice that the
t 0
Fig.7 AMS-latch mode without initial input signal.
t 3 t 4
t r
t 5 t 6
t f
t d
r
t 7
in
is
.
13
A latch forces the AMS output to be HIGH until a signal
appears at V
output any more until AMS-latch mode is started again.
The existence of the latch appears necessary if the AMS
output for example drives a stop solenoid via a power FET.
The LOW output level will cause a drive of the stop
solenoid. This would happen after a maximum time of t
occurred without any input signal. If there is no music on
tape for a long time (e.g. at tape end), the AMS mode
would be activated repeatedly as long as there is no signal
at V
detecting the pauses.
t 8 t 9 t 10
t b t r
in
. Thus the circuit waits until first music appears before
t 11 t 12
in
(t
4
). After t
t 13 t 14
t p t d
4
the latch will not affect the
t 15
V l : voltage at
pin 3 (CONTRA)
V t : voltage at
pin 22 (CONTRB)
level detector
input
time detector
input
Preliminary specification
MED627
TEA0675
t
t
t
t
t
d