TDA7491MV Datasheet, PDF (23/28 Pages) STMicroelectronics – 25 W mono BTL class-D audio amplifier

TDA7491MV
Application information
7.5
Filterless modulation
The output modulation scheme of the BTL is called unipolar pulse width modulation (PWM).
The differential output voltages change between 0 V and +V_CC and between 0 V and -V_CC.
This is in contrast to the traditional bipolar PWM outputs which change between +V_CC
and -V_CC.
An advantage of this scheme is that it effectively doubles the switching frequency of the
differential output waveform. The OUTP and OUTN are in the same phase when the input is
zero, then the switching current is low and the loss in the load is small. In practice, a short
delay is introduced between these two outputs in order to avoid the BTL output switching at
the same time.
TDA7491MV can be used without a filter before the speaker, because the frequency of the
TDA7491MV output is beyond the audio frequency, the audio signal can be recovered by the
inherent inductance of the speaker and natural filter of the human ear.
Figure 23. Unipolar PWM output
INP
INN
OUTP
OUTN
Differential
OUT
Doc ID 14576 Rev 2
23/28