Texas Instruments TPA 311 manual Signal Routing, Signal Conditioning, Headphone Output Jack

Using The TPA311 EVM With the Plug-N-Play Evaluation Platform

3.3.2Signal 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
Audio	U1
	Signal
Input
	Conditioning
L

Off

S2

On

U3			+
TPA311	R		R
Amplifier EVM			±	J7, J8, J9
				Speaker
U4			±	Outputs
TPA311	L		L
Amplifier EVM			+
	U2 ± U4
			R
U5	R		+
Stereo		GND	±	J10
Headphone	S3			Headphone
Amplifier	L		±	Output
			+
			L
	U5

3.3.2.1Signal 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

3.3.2.2Headphone 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).

JTo keep the TPA311 amplifier outputs separated, set switch S3 to the headphone amplifier position (U5 ) and use the speaker outputs (J7, J8, and J9)

JTo route the TPA311 amplifier outputs to the headphone output jack (J10), set switch S3 to the power amplifier position (U2 ± U4 ) Ð use this setting only if the TPA311 EVMs are to drive single-ended loads connected to J10

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