Texas Instruments TPA0242 - Manual (Page 21)

The TPA0242 Audio Power Amplifier Evaluation Module
3-5 Details
Figure 3–4. TPA0242 Amplifier IC
MUX
SE/BTL
MUX
HP/LINE
VOLUME
CONTROL
PC BEEP
L LINE
L HP
VOLUME PC BEEP
L IN
R HP
R LINE
R IN
3.2.2 Inputs and Gain
Each channel has two separate signal inputs, line and headphone (HP ), that
are automatically selected with the output mode (SE/BTL). An input multi-
plexor in the amplifier IC selects the HP inputs when the IC is in the SE output
mode and the line inputs when in the BTL output mode.
Line and headphone inputs share common positive inputs. If using separate
line and headphone inputs, R IN and L IN should be AC grounded through a
capacitor. If using differential inputs, line and headphone inputs must be the
same.
A third input, PC BEEP, is common to both channels. The TPA0242 IC
monitors this input when operating in both the active and shutdown modes and
automatically switches to this input when a signal is sensed. In computer
applications, for example, this allows the normal audio signal (music, sounds,
etc.) to be interrupted when there is a need to output a computer beep. When
the beep signal ends, the IC switches back to the previous mode.
The PC BEEP input gain is approximately 1/4 V/V, and requires an input signal
greater than 1 V peak-to-peak in order to detect the signal. Setting PCB
ENABLE high forces the TPA0242 IC into the PC BEEP mode, regardless of
the amplitude of the signal applied to the PC BEEP input.