Texas Instruments TPA311 - Manual (Page 21)

Using The TPA311 EVM With the Plug-N-Play Evaluation Platform
3-7 Details
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
U1
Signal
Conditioning
On
Off
U5
Stereo
Headphone
Amplifier
S2
R
L
R
L
L
U5
U2 – U4
S3
J10
Headphone
Output
R
L
Audio
Input
R
L
J7, J8, J9
Speaker
Outputs
R
+
+
–
–
U3
TPA311
Amplifier EVM
+
+
–
–
U4
TPA311
Amplifier EVM
GND
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.
- Switch S2 selects signal conditioning or bypasses it
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
µ
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).
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