The TPA3139D2 device integrates a circuitry which protects the speakers from DC current that might occur due to defective capacitors on the input or shorts on the printed circuit board at the inputs. A DC detect fault is reported on the SD/ FAULT pin as a low state. The DC Detect fault also causes the amplifier to shutdown by changing the state of the outputs to Hi-Z.

A DC Detect Fault is issued when the output DC voltage sustain for more than 800 msec at the same polarity. This feature protects the speaker from large DC currents or AC currents less than 1 Hz. To avoid nuisance faults due to the DC detect circuit, hold the SD/ FAULT pin low at power-up until the signals at the inputs are stable. Also, take care to match the impedance seen at the positive and negative inputs to avoid nuisance DC detect faults.