Platform Signal Routing And Outputs - Texas Instruments TPA311 User Manual

3.3.2 Signal Routing
Signal flow on the platform is controlled by two signal routing switches, as
shown in Figure 3 – 5.
Figure 3–5. Platform Signal Routing and Outputs
R
U1
Audio
Signal
Input
Conditioning
L
3.3.2.1 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 TPA311 power amplifiers.
3.3.2.2 Headphone Output Jack
Switch S3 is the source select for the stereo headphone output jack, J10. The
headphone jack is capacitively coupled (via 470 F electrolytics) and can
output either the signal from the headphone amplifier in socket U5, or the
signal from the TPA311 power amplifiers installed in sockets U3 and U4, 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 TP311 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 sockets to shut down the TPA311 EVMs 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).
Using The TPA311 EVM With the Plug-N-Play Evaluation Platform
Off
U3
TPA311
Amplifier EVM
S2
U4
TPA311
Amplifier EVM
On
U5
Stereo
Headphone
Amplifier
Switch S2 selects signal conditioning or bypasses it
J
To keep the TPA311 amplifier outputs separated, set switch S3 to the
headphone amplifier position (U5) and use the speaker outputs (J7,
J8, and J9)
J
To route the TPA311 amplifier outputs to the headphone output jack
(J10), set switch S3 to the power amplifier position (U2 – U4 ) — use
this setting only if the TPA311 EVMs are to drive single-ended loads
connected to J10
+
R R
–
–
L L
+
U2 – U4
R
+
R
–
GND
S3
L
–
+
L
U5
Details
J7, J8, J9
Speaker
Outputs
J10
Headphone
Output
3-7