Datasheet

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SE/BTL
ROUT+ 20
RIN+
4
5 RIN-
ROUT- 2
1 kW
C
O
330 Fm
100 kW
19
100 kW
V
DD
_
+
_
+
Bypass
_
+
Bypass
EN
_
+
Bypass
LOUT+
SHUTDOWN MODES
FADE OPERATION
TPA6021A4
SLOS465 – JUNE 2005
APPLICATION INFORMATION (continued)
Figure 21. TPA6021A4 Resistor Divider Network Circuit
Using a 1/8-in. (3,5 mm) stereo headphone jack, the control switch is closed when no plug is inserted. When
closed the 100-k Ω /1-k Ω divider pulls the SE/ BTL input low. When a plug is inserted, the 1-k Ω resistor is
disconnected and the SE/ BTL input is pulled high. When the input goes high, the OUT– amplifier is shut down
causing the speaker to mute (open-circuits the speaker). The OUT+ amplifier then drives through the output
capacitor (C
o
) into the headphone jack.
The TPA6021A4 employs a shutdown mode of operation designed to reduce supply current (I
DD
) to the absolute
minimum level during periods of nonuse for power conservation. The SHUTDOWN input terminal should be held
high during normal operation when the amplifier is in use. Pulling SHUTDOWN low causes the outputs to mute
and the amplifier to enter a low-current state, I
DD
= 20 µA. SHUTDOWN should never be left unconnected
because amplifier operation would be unpredictable.
Table 1. SE/ BTL and Shutdown Functions
INPUTS
(1)
AMPLIFIER STATE
SE/ BTL SHUTDOWN OUTPUT
X Low Mute
Low High BTL
High High SE
(1) Inputs should never be left unconnected.
For design flexibility, a fade mode is provided to slowly ramp up the amplifier gain when coming out of shutdown
mode and conversely ramp the gain down when going into shutdown. This mode provides a smooth transition
between the active and shutdown states and virtually eliminates any pops or clicks on the outputs.
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