DocID024368 Rev 3

19/24

STPA002

General information

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5.4

Warnings

5.4.1

DC offset detection (OD pin)

The STPA002 integrates a DC offset detector to avoid that an anomalous input DC offset is

multiplied by the amplifier gain producing a dangerous large offset at the output. In fact an

output offset may lead to speakers damage for overheating. To correctly detect a DC offset,

the power amplifier has to be un-muted with no input signal.

When the differential output voltage is out of a window comparator with thresholds ± 2 V

(typ), the OD pin is pulled down.

5.4.2

Clipping detection and diagnostics (CD-DIAG pin)

When clipping occurs, the output signal is distorted. If the signal distortion on one of the

output channels exceeds 1 %, the CD-DIAG pin is pulled down. This information can be

sent to an audio processor in order to reduce the input signal of the amplifier and reduce the

clipping. Thanks to a particular internal circuitry, the clip detector is always functional till 7 V.

A short to ground and short to Vcc is signaled by CD-DIAG. This pin is pulled down to

ground till these shorts are present to inform the user a protection occurred.

CD-DIAG acts also as thermal warning. In fact every time Tj exceeds 140 °C, it is pulled

down to notify this occurrence.

Figure 26. Audio section waveforms