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Philips Semiconductors
TDA8920B_2
Product data sheet
The amplifier system can be switched to one of three operating modes by pin MODE:
•
Standby mode; with a very low supply current
•
Mute mode; the amplifiers are operational; but the audio signal at the output is
suppressed by disabling the VI-converter input stages
•
Operating mode; the amplifiers are fully operational with output signal
To ensure pop noise-free start-up, the DC output offset voltage is applied gradually to the
output at a level between Mute mode and Operating mode levels. The bias current setting
of the VI converters is related to the voltage on the MODE pin; in Mute mode the bias
current setting of the VI converters is zero (VI converters disabled) and in Operating mode
the bias current is at maximum. The time constant required to apply the DC output offset
voltage gradually between Mute and Operating mode levels can be generated via an
RC-network on the MODE pin. An example of a switching circuit for driving pin MODE is
illustrated in
Figure
4. If the capacitor C is left out of the application the voltage on the
MODE pin will be applied with a much smaller time-constant, which might result in audible
pop noises during start-up (depending on DC output offset voltage and loudspeaker
used).
In order to fully charge the coupling capacitors at the inputs, the amplifier will remain
automatically in the Mute mode before switching to the Operating mode. A complete
overview of the start-up timing is given in
Fig 4. Example of mode selection circuit
Rev. 02 — 07 November 2005
Figure
5.
+ 5 V
standby/
mute
R
R
C
mute/on
TDA8920B
2 × 100 W class-D power amplifier
MODE pin
SGND
001aab172
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
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