Texas Instruments TPA0242 - Manual (Page 28)

Using The TPA0242 EVM With the Plug-N-Play Evaluation Platform
3-12 Details
3.3.4 Mute (Shutdown)/Mode
The TPA0242 EVM is equipped with a shutdown control input pin. When this
input is pulled to ground, the TPA0242 amplifier IC on the module enters the
shutdown mode and dissipates very little power. While in the shutdown mode,
the PC BEEP input is still active. When the EVM control input is tied to GND
or allowed to float, normal 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 to conserve
power.
A mode control input pin on the EVM switches the TPA0242 amplifier IC
between the bridge-tied load (BTL) output mode and the single-ended (SE)
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 TPA0242 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.
3.3.4.1 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 – 7).
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
DD
through a
240-
Ω
resistor (R3) depending on whether a plug is inserted in J10 or not.
Figure 3–7. Mute/Mode and Polarity Control
J10
Headphone
Jack
R3
240
Ω
R4
1 k
Ω
R5
1 k
Ω
JP8 JP6
U2
Power
Amplifier
Lo
Hi
Polarity
Mode
Mute
VDD
SPK
(U2–U4)