Texas Instruments SLOU121 - Manual (Page 33)

Using the TPA6011A4 EVM With the Plug-N-Play Evaluation Platform
3-13 Details
3.3.3.1 Signal Conditioning
The audio signal from the input jacks can be applied to the signal conditioning
socket (U1) if an EVM is installed there, or socket U1 can be bypassed and the
audio input signal applied directly to the inputs of the TPA6011A4.
- Switch S2 selects signal conditioning or bypasses it.
3.3.3.2 Headphone Output Jack
Switch S3 is the source select for the stereo headphone output jack, J10. The
headphone jack is capacitively coupled (via 470-
µ
F electrolytics) and can
output either the signal from the headphone amplifier in socket U5, or the
signal from the TPA6011A4 power amplifier installed in socket U2, as
determined by the setting of headphone source select switch S3.
When S3 is set to the power amplifier position (U2 – U4), the headphone jack
is connected to the TPA6011A4 power amplifier OUT+ output lines. When a
plug is inserted into the jack, signals output through J10 are returned to
platform ground, requiring single-ended power amplifier operation. A switch
inside the headphone jack produces a control signal that can be routed to the
power amplifier socket to shut down the TPA6011A4 EVM or switch it to
single-ended output mode when a plug is inserted.
Source select switch S3 connects the headphone jack to the output lines of
either the headphone amplifier socket U5, or the power amplifier sockets
(U2 – U4).
- To keep the TPA6011A4 amplifier outputs separated, set switch S3 to the
headphone amplifier position (U5 ) and use the speaker outputs (J7, J8,
and J9).
- To route the TPA6011A4 amplifier outputs to the headphone output jack
(J10), set switch S3 to the power amplifier position (U2 – U4 ). Uuse this
setting only if the TPA6011A4 EVM is to drive single-ended loads con-
nected to J10.
3.3.4 Mute (Shutdown)/Mode
The TPA6011A4 EVM is equipped with a shutdown control input pin. When this
input is pulled to ground, the TPA6011A4 amplifier IC on the module enters the
shutdown mode and dissipates very little power. While in the shutdown mode,
the PC BEEP input is still active. When the EVM control input is tied to GND
or allowed to float, normal amplifier operation resumes.
In typical applications, as often found in notebook computers, portable audio
products, and such, the internal speakers mute when headphones are
plugged into the headphone jack, or internal speakers mute when external
speakers are connected. In applications using separate speaker and
headphone amplifiers, the one not being used can be shut down to conserve
power.
A mode control input pin on the EVM switches the TPA6011A4 amplifier IC
between the bridge-tied load (BTL) output mode and the single-ended (SE)