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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
DD
, 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 V
DD
, 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-kΩ resistor to ground (R4 and R5). The
switch in the headphone jack pulls one line or the other up to V
DD
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 kΩ
R5
1 kΩ
JP8 JP6
U3, U4
Power
Amplifiers
Lo
Hi
Polarity
Mode
Mute
V
DD
SPK
(U2–U4)