Texas Instruments TPA301 User Manual download pdf (Page 21)

Using The TPA301 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

Signal

Conditioning

Off

Stereo

Headphone

Amplifier

U2–U4

J10

Headphone

Output

Audio

Input

J7, J8, J9

Speaker

Outputs

–

TPA301

Amplifier EVM

–

TPA301

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 TPA301 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 µF electrolytics) and can

output either the signal from the headphone amplifier in socket U5, or the

signal from the TPA301 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 TP301 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 TPA301 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).

To keep the TPA301 amplifier outputs separated, set switch S3 to the

headphone amplifier position (U5) and use the speaker outputs (J7,

J8, and J9)

To route the TPA301 amplifier outputs to the headphone output jack

(J10), set switch S3 to the power amplifier position (U2 – U4) and

reverse the jumper on JP8 to prevent muting of the TPA301 module

when a plug is inserted into J10 — use this setting only if the TPA301

EVMs are to drive single-ended loads connected to J10

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Texas Instruments TPA301 User Manual Page 21

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