General information

STPA003

20/25

DS10473 Rev 2

5.4

Warnings

5.4.1

DC offset detection (OD pin)

The STPA003 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 ± 3 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.

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

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

down to notify this occurrence.

Figure 27. Audio section waveforms

t

t

t

MUTE PIN

VOLTAGE

Vs

OUTPUT

WAVEFORM

DIAG pin

WAVEFORM

SHORT TO GND

OR TO Vs

CLIPPING

THERMAL

PROXIMITY

ST-BY PIN

VOLTAGE

t

GAPGPS00712