Texas Instruments TPA0242 manual Signal Routing, Signal Conditioning, Headphone Output Jack

Using The TPA0242 EVM With the Plug-N-Play Evaluation Platform

3.3.3Signal Routing

Signal flow on the platform is controlled by two signal routing switches, as shown in Figure 3±6.

Figure 3±6. Platform Signal Routing and Outputs

R
Audio	U1
	Signal
Input
	Conditioning
L

Off

S2

On

			+
	R		R
U2			±	J7, J8, J9
TPA0242
				Speaker
Amplifier EVM
			±	Outputs
	L		L
			+
	U2 ± U4
			R
U5	R		+
Stereo		GND	±	J10
Headphone	S3			Headphone
Amplifier	L		±	Output
			+
			L
	U5

3.3.3.1Signal 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 TPA0242.

-Switch S2 selects signal conditioning or bypasses it.

3.3.3.2Headphone 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 TPA0242 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 TPA0242 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 TPA0242 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).

JTo keep the TPA0242 amplifier outputs separated, set switch S3 to the headphone amplifier position (U5 ) and use the speaker outputs (J7, J8, and J9)

JTo route the TPA0242 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 TPA0242 EVM is to drive single-ended loads connected to J10

Details 3-11