TAS5754M_15 Datasheet, PDF (90/127 Pages) Texas Instruments – Digital Input, Closed-Loop Class-D Amplifier with HybridFlow Processing

TAS5754M
SLAS987 – JUNE 2014
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9.2.2 Mono (PBTL) Systems
For the mono (PBTL) PCB layout, see Figure 89.
A mono system refers to a system in which the amplifier is used to drive a single loudspeaker. Parallel Bridge
Tied Load (PBTL) indicates that the two full-bridge channels of the device are placed in parallel and drive the
loudspeaker simultaneously using an identical audio signal. The primary benefit of operating the TAS5754M
device in PBTL operation is to reduce the power dissipation and increase the current sourcing capabilities of the
amplifier output. In this mode of operation, the current limit of the audio amplifier is approximately doubled while
the on-resistance is approximately halved.
The loudspeaker can be a full-range transducer or one that only reproduces the low-frequency content of an
audio signal, as in the case of a powered subwoofer. Often in this use case, two stereo signals are mixed
together and sent through a low-pass filter in order to create a single audio signal which contains the low
frequency information of the two channels. Conversely, advanced digital signal processing can create a low-
frequency signal for a multichannel system, with audio processing which is specifically targeted on low-frequency
effects.
Although any of the HybridFlows can be made to work with a mono speaker, it is strongly recommended that
HybridFlows which have been created specifically for mono applications be used. These HybridFlows contain the
mixing and filtering required to generate the mono signal. They also include processing which is targeted at
improving the low-frequency performance of an audio system- a feature that, while targeted at subwoofers, can
also be used to enhance the low-frequency performance of a full-range speaker.
Because low-frequency signals are not perceived as having a direction (at least to the extent of high-frequency
signals) it is common to reproduce the low-frequency content of a stereo signal that is sent to two separate
channels. This configuration pairs one device in Mono PBTL configuration and another device in Stereo BTL
configuration in a single system called a 2.1 system. The Mono PBTL configuration is detailed in the 2.1 (Stereo
BTL + External Mono Amplifier) Systems section.
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