Texas Instruments TPA 311 manual ±6. Mute/Mode and Polarity Control, Details

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

3.3.3Mute/Mode

The TPA311 EVM is equipped with a mute (shutdown) control input pin. When this input is tied to VDD, the TPA311 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.

A mode control input pin on the EVM switches the TPA311 amplifier IC between the bridge-tied load (BTL) output mode and the single-ended output mode. When the mode control input is tied to GND, the module operates in the BTL output mode. When this input is tied to VDD, the module operates in the single-ended output mode.

In the typical application, output mode switching allows the TPA311 to operate in the BTL output mode for increased power to internal speakers and then switch to single-ended mode to drive headphones when a plug is inserted into the headphone jack.

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 a plug is inserted in J10 or not.

Figure 3±6. Mute/Mode and Polarity Control

	VDD
	R3	Polarity
	240 Ω
		JP8
J10		Lo

Headphone

Jack		Hi
R4	R5
		SPK
1 kΩ	1 kΩ	(U2±U4)

JP6

Mode	U3, U4
	Power
	Amplifiers
Mute

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