Texas Instruments MIXED SIGNAL PRODUCTS TPA0103 - Manual (Page 26)

Using The TPA0103 EVM With the Plug-N-Play Evaluation Platform
3-12 Details
3.3.4 Mode Control
The TPA0103 EVM is equipped with a mode control input pin that receives a
control signal from the platform. This EVM pin is connected to the amplifier IC
Mode A output mode control input pin. The state of this input, in conjunction
with the state of the Mode B output mode control input pin, controls the output
mode of the amplifier IC on the EVM.
When the EVM mode control input pin (Mode A) is high, the TPA0103 amplifier
IC on the module either enters the mute mode and dissipates very little power
when Mode B jumper S2 on the EVM is set to OFF. When S2 is set to ON, a
high on the EVM mode control input pin causes the amplifier IC to enter the
L/R stereo outputs only mode.
When the EVM mode control input is tied to GND or allowed to float, the
3-channel output mode is selected if S2 is set to OFF and the center channel
only output mode is selected if S2 is set to ON.
In the typical application, output mode switching allows the TPA0103 to
operate the BTL center channel to drive a speaker and then switch to stereo
left and right 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)