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Short-circuit Diodes for TPA300x Class-D Amplifiers
Several of the TPA300x series Class-D audio power amplifiers require external diodes to ground from their outputs to provide full short circuit protection. These are required to prevent damage to body diodes of the low-side output devices. Body diodes of high-side output devices are robust enough to handle short circuit currents directly, so no diodes are required from the outputs to the power supply.
These diodes must be capable of handling the voltages and currents to which they can be exposed. If they are not, they may short or open, and then they may disable an APA circuit, and they can permit or cause further damage. They must have low forward voltage at peak currents of 1A and greater, sothey must be Schottkys. Short circuits can generate currents as high as 10 to 15 A with high power supply voltages, so the Schottky diode must handle surge currents of this magnitude for periods of a few microseconds. Naturally, the peak reverse voltage rating of the diode must be greater than the power supply voltage.
For this reason TI recommends using a diode like the B130-13 from Diodes, Inc. This diode is used generally in TI EVMs for these parts. B130-13 is a Schottky diode with 30V reverse voltage rating and 30A peak current rating over 8.3mS. B130-13 also is an SMD component. A different diode may be used, but it must have characteristics similar to those of B130-13 to be successful.
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