Philips TDA1562Q Application Note page 53

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Philips Semiconductors

The situation changes dramatically when the lift capacitors are discharged. In that

situation the amplifier will already be damaged by a voltage pulse of 12V at one of the

outputs. This is shown in fig. 41.

a. No damage to TDA1562

Fig 41. Current flowing into amplifier with positive pulse at output, Ch2 (cyan): Voutput, Ch3 (magenta) : current

into device

Normally, protecting an amplifier from voltage pulses at the outputs can be done by

connecting a diode from each output to the supply rail. In the TDA1562 this method

cannot be applied because during normal operation the output voltage can exceed the

supply voltage.

Since in most cases the +terminal of the lift capacitors is the connection with the highest

voltage in the application, the most effective way to protect the output against positive

pulses seemed to be to connect a diode between the output and the +terminal of the lift

capacitors.

This, however, did not give the desired effect. After more testing it was found that an

additional Schottky diode between the negative terminal of the lift capacitor and the

supply rail did give the desired results. The resulting circuit is shown in fig. 42.

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Application note

5A/div

Rev. 01.02 — 05 May 2006

TDA1562Q application note

b. TDA1562 damaged

AN<nnnnn>

10A/div.

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