TDA8920B_2
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
Product data sheet
Rev. 02 — 07 November 2005
9 of 34
Philips Semiconductors
TDA8920B
2
×
100 W class-D power amplifier
In case of an impedance drop (e.g. due to dynamic behavior of the loudspeaker) the same
protection will be activated; the maximum output current is again limited to 8 A, but the
amplifier will NOT switch-off completely (thus preventing audio holes from occurring).
Result will be a clipping output signal without any artefacts.
See also
for more information on this maximum output current limiting
feature.
8.3.3 Window Protection (WP)
During the start-up sequence, when pin MODE is switched from standby to mute, the
conditions at the output terminals of the power stage are checked. In the event of a
short-circuit at one of the output terminals to V
DD
or V
SS
the start-up procedure is
interrupted and the system waits for open-circuit outputs. Because the test is done before
enabling the power stages, no large currents will flow in the event of a short-circuit. This
system is called Window Protection (WP) and protects for short-circuits at both sides of
the output filter to both supply lines. When there is a short-circuit from the power PWM
output of the power stage to one of the supply lines (before the demodulation filter) it will
also be detected by the start-up safety test. Practical use of this test feature can be found
in detection of short-circuits on the printed-circuit board.
Remark: This test is operational during (every) start-up sequence at a transition between
Standby and Mute mode. However when the amplifier is completely shut-down due to
activation of the OverCurrent Protection (OCP) because a short to one of the supply lines
occurred, then during restart (after 100 ms) the window protection will be activated. As a
result the amplifier will not start-up until the short to the supply line is removed.
