Texas Instruments SLOU025 manual 3.3.3Shutdown, ±6. Shutdown Polarity Control, Details

Using The TPA122 MSOP EVM With the Plug-N-Play Evaluation Platform

3.3.3Shutdown

The TPA122 MSOP EVM is equipped with a shutdown control input pin. When this input is tied to VDD, the TPA122 amplifier IC on the module ceases operation and enters an ultra-low-power state. When the EVM shutdown 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 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 or removed (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.

Figure 3±6. Shutdown Polarity Control

VDD
R3		Polarity
240 Ω
		JP7
J10		Lo	Shutdown	U5
Headphone				Headphone
Jack		Hi		Amplifier
R4	R5
		HP
1 kΩ	1 kΩ	(U5)

3.3.3.2Shutdown Polarity Select (JP7)

A 3-pin jumper header (JP7) on the platform selects the shutdown control signal polarity by connecting either the active-high or the active-low line from the headphone jack to platform socket U5. The TPA122 MSOP EVM shuts down when VDD is applied to the module SD pin.

JTo shut down the TPA122 MSOP amplifier module when a plug is inserted into the headphone jack, jumper JP7 to Hi.

JTo shut down the TPA122 MSOP amplifier module until a plug is inserted into the headphone jack, jumper JP7 to Lo (this is the typical setting).

3-8 Details