Texas Instruments TPA311 User Manual

Page 22

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

3-8

Details

3.3.3

Mute/Mode

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

, the TPA311 amplifier IC on the module shuts down and

assumes an ultralow-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 V

, 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.

3.3.3.1

Headphone 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-k

Ω

resistor to ground (R4 and R5). The

switch in the headphone jack pulls one line or the other up to V

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

J10

Headphone

Jack

R3
240

Ω

R4
1 k

Ω

R5
1 k

Ω

JP8

JP6

U3, U4

Power

Amplifiers

Polarity

Mode

Mute

VDD

SPK

(U2–U4)