TDA8929T Datasheet, PDF (10/36 Pages) NXP Semiconductors – Controller class-D audio amplifier

Philips Semiconductors
Controller class-D audio amplifier
Preliminary specification
TDA8929T
8.3.3 START-UP SAFETY TEST
During the start-up sequence, when pin MODE is switched
from standby to mute, the condition at the output terminals
of the power stage are checked. These are the same lines
as the feedback inputs of the controller. In the event of a
short-circuit of one of the output terminals to V_DD or V_SS
the start-up procedure is interrupted and the system waits
for non-shorted 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 protects against
short-circuits at both sides of the output filter to both supply
lines. When there is a short-circuit from the outputs 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 from this test feature can be
found in detection of short-circuits on the printed-circuit
board.
Remark: this test is only operational prior to or during the
start-up sequence, and not during normal operating.
8.4 Differential audio inputs
For a high common mode rejection and a maximum
flexibility of application, the audio inputs are fully
differential. By connecting the inputs anti-parallel the
phase of one of the channels is inverted, so that a load can
be connected between the two output filters. In this case
the system operates as a mono BTL amplifier (see Fig.5).
Also in the stereo single-ended configuration it is
recommended to connect the two differential inputs in
anti-phase. This has advantages for the current handling
of the power supply at low signal frequencies.
handbook, full pagewidth
Vi
IN1 +
IN1 −
TDA8929T
IN2 +
IN2 −
CONTROLLER
REL1
SW1
EN1
EN2
SW2
REL2
OUT1
POWER
STAGE
SGND
OUT2
MGW185
2001 Dec 11
Fig.5 Mono BTL application.
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