Texas Instruments TPA701 3.3.2Signal Routing, ±5. Platform Signal Routing and Outputs, Details

Using The TPA701 MSOP 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			+
TPA701	R		R
Amplifier EVM			±	J7, J8, J9
				Speaker
U4			±	Outputs
TPA701	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 TPA701 power amplifiers.

-Switch S2 selects signal conditioning or bypasses it

3.3.3Mute/Mode

The TPA701 MSOP EVM is equipped with a shutdown (mute) control input pin. When this input is tied to VDD, the TPA701 amplifier IC on the module shuts down and assumes an ultra-low power mode. When the EVM control input is tied to GND or allowed to float, amplifier operation resumes.

In typical applications, as often found in notebook computers, portable audio products, and such, the internal speakers mute when headphones are plugged into the headphone jack, or internal speakers mute when external speakers are connected. In applications using separate speaker and headphone amplifiers, the one not being used can be shut down (muted) to conserve power.

3.3.3.1Headphone Jack Control Signals

The platform headphone output jack (J10) contains an internal switch that changes the state of a pair of control lines when a plug is inserted (Figure 3±6). Each control line is pulled down by a 1-kΩresistor to ground (R4 and R5). The switch in the headphone jack pulls one line or the other up to VDD through a 240 Ω resistor (R3) depending on whether or not a plug is inserted in J10.

Details 3-7