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Using The TPA005D12 Class-D EVM With the Plug-N-Play Platform
3-14
Details
3.4.4 Shutdown
The TPA005D12 class-D EVM is equipped with a shutdown control input pin.
When this input is tied to GND, the TPA005D12 amplifier IC on the module
enters the shutdown mode and dissipates very little power. When the EVM
control input is tied to V
DD
or allowed to float, amplifier operation resumes.
In typical applications, as often found in notebook computers and other
portable audio products, 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.
The TPA005D12 EVM shutdown control pin connects to the platform Mute line
of JP6 when the EVM is inserted in the plug-n-play platform. When JP6 is set
to Mute and JP8 is set to Lo, the class-D EVM will operate normally until a
headphone plug is inserted into platform jack J10 and the class-D amplifier is
placed into shutdown. Once the jack is removed from J10, the class-D EVM
again becomes active. Note that when JP6 is set to mute and the class-D EVM
shutdown pin is activated, the platform current increases by approximately 20
mA. This current is set by the connection of the 240-Ω platform resistor (R3)
to ground through the EVM shutdown switch.
3.4.4.1 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 3–8).
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 3–8. Mute/Mode and Polarity Control
J10
Headphone
Jack
R3
240 Ω
R4
1 kΩ
R5
1 kΩ
JP8 JP6
U2
Power
Amplifier
Lo
Hi
Polarity
Mode
Mute
V
DD
SPK
(U2–U4)