7.4 Device Functional Modes

7.4.1 MODE_SEL = LOW: BD Modulation

This is a modulation scheme that allows operation without the classic LC reconstruction filter when the amp is

driving an inductive load with short speaker wires. Each output is switching from 0 volts to the supply voltage.

The OUTPx and OUTNx are in phase with each other with no input so that there is little or no current in the

speaker. The duty cycle of OUTPx is greater than 50% and OUTNx is less than 50% for positive output voltages.

The duty cycle of OUTPx is less than 50% and OUTNx is greater than 50% for negative output voltages. The

voltage across the load sits at 0 V throughout most of the switching period, reducing the switching current, which

reduces any I2R losses in the load.

OUTP

OUTN

OUTP

-OUTN

Speaker

Current

OUTP

OUTN

OUTP-OUTN

Speaker

Current

OUTP

OUTN

OUTP

-OUTN

Speaker

Current

0 V

0 V

PVCC

No Output

Positive Output

Negative Output

0 A

0 A

0 V

- PVCC

Figure 7-2. BD Mode Modulation

TPA3139D2

SLOS810A – OCTOBER 2019 – REVISED AUGUST 2020

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