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Using The TPA301 EVM With the Plug-N-Play Evaluation Platform
3-8
Details
3.3.3 Muting
The TPA301 EVM is equipped with a mute (shutdown) control input pin. When
this input is tied to V
DD
, the TPA301 amplifier IC on the module shuts down and
assumes an ultra-low power mode. When the control input is tied to GND or
allowed to float, amplifier operation resumes.
The typical application, as often found in notebook computers, portable audio
products, and such, would have the internal speakers mute when headphones
are plugged into the headphone jack, or have 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.
3.3.3.1 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. 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).
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)
3.3.3.2 Mute Polarity Select (JP8)
A three-pin jumper header (JP8), functioning as a SPDT switch, selects the
control signal polarity by connecting either the active-low or the active-high line
from the headphone jack to jumper JP6.
To mute the TPA301 amplifier module when a plug is inserted into the
headphone jack, jumper JP8 to Hi.
To mute the TPA301 amplifier module until a plug is inserted into the
headphone jack, jumper JP8 to Lo.
3.3.3.3 Mute Select (JP6)
A second three-pin jumper header (JP6) routes the control signal from the
headphone jack to either the mute or the mode pin of the evaluation module.
To mute the TPA301 amplifier module when a plug is inserted into the
headphone jack, jumper JP6 to MUTE.
To not affect the TPA301 amplifier when a plug is inserted into the
headphone jack, jumper JP6 to MODE or leave JP6 unjumpered.