DocID023043 Rev 7

19/26

STPA001

General information

25

4.4

Warnings

4.4.1

DC offset detection (OD pin)

The STPA001 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. The detector works with the

amplifier un-muted and no signal at the inputs.

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

(typ), the OD pin is pulled down.

4.4.2

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

6.5 V.

A short to ground and short to Vcc is pointed out by CD-DIAG. This pin is pulled down to 0 V

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