TEA0679 NXP Semiconductors, TEA0679 Datasheet - Page 11

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

Philips Semiconductors
Short description of music search
A system for music search consists mainly of a level and a
time detection circuit (see Fig.4). For adapting and
decoupling the input signal is amplified (A), then rectified
(B) and smoothed with a time constant (C). Thus the
voltage at (C) corresponds to the signal level and will be
compared to the predefined pause level at the first
comparator (D), the level detector. If the signal level
becomes smaller than the pause level, the level detector
changes its output signal. Due to the output level of the
level detector the capacitor of the second time constant (E)
will be charged, respectively discharged.
1998 Nov 12
handbook, full pagewidth
I
reduction circuit for playback applications
2
C-bus controlled dual Dolby* B-type noise
INPUT
AMPLIFIER
(A)
RECTIFIER
(B)
Fig.4 Integrated music search function.
(C)
t 1
V I
LEVEL DETECTOR
COMPARATOR 1
11
If the pause level of the input signal remains for a certain
time period, the voltage at the capacitor reaches a certain
value, which corresponds to an equivalent time value.
The voltage at the capacitor will be compared to a
predefined time-equivalent voltage by the second
comparator (F), the time detector. If the pause level of the
input signal remains for this predefined time, the time
detector changes its output level to pause found status.
(D)
(E)
t 2
V t
TIME DETECTOR
COMPARATOR 2
(F)
Product specification
TEA0679T
MED624
OUTPUT