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ROUT+
Device Shutdown
ROUT+
Device Shutdown
VOLUME, SEDIFF, AND SEMAX OPERATION
TPA6011A4
SLOS392A – FEBRUARY 2002 – REVISED JULY 2004
Figure 31. Shutdown Sequence in the
Figure 32. Shutdown Sequence in the
Fade-on Mode
Fade-off Mode
Three pins labeled VOLUME, SEDIFF, and SEMAX control the BTL volume when driving speakers and the SE
volume when driving headphones. All of these pins are controlled with a dc voltage, which should not exceed
V
DD
.
When driving speakers in BTL mode, the VOLUME pin is the only pin that controls the gain. Table 1 shows the
gain for the BTL mode. The voltages listed in the table are for V
DD
= 5 V. For a different V
DD
, the values in the
table scale linearly. If V
DD
= 4 V, multiply all the voltages in the table by 4 V/5 V, or 0.8.
The TPA6011A4 allows the user to specify a difference between BTL gain and SE gain. This is desirable to avoid
any listening discomfort when plugging in headphones. When switching to SE mode, the SEDIFF and SEMAX
pins control the singe-ended gain proportional to the gain set by the voltage on the VOLUME pin. When SEDIFF
= 0 V, the difference between the BTL gain and the SE gain is 6 dB. Refer to the section labeled bridged-tied
load versus single-ended load for an explanation on why the gain in BTL mode is 2x that of single-ended mode,
or 6dB greater. As the voltage on the SEDIFF terminal is increased, the gain in SE mode decreases. The voltage
on the SEDIFF terminal is subtracted from the voltage on the VOLUME terminal and this value is used to
determine the SE gain.
Some audio systems require that the gain be limited in the single-ended mode to a level that is comfortable for
headphone listening. Most volume control devices only have one terminal for setting the gain. For example, if the
speaker gain is 20 dB, the gain in the headphone channel is fixed at 14 dB. This level of gain could cause
discomfort to listeners and the SEMAX pin allows the designer to limit this discomfort when plugging in
headphones. The SEMAX terminal controls the maximum gain for single-ended mode.
The functionality of the SEDIFF and SEMAX pin are combined to set the SE gain. A block diagram of the
combined functionality is shown in Figure 33. The value obtained from the block diagram for SE_VOLUME is a
dc voltage that can be used in conjunction with Table 2 to determine the SE gain. Again, the voltages listed in
the table are for V
DD
= 5 V. The values must be scaled for other values of V
DD
.
Table 1 and Table 2 show a range of voltages for each gain step. There is a gap in the voltage between each
gain step. This gap represents the hysteresis about each trip point in the internal comparator. The hysteresis
ensures that the gain control is monotonic and does not oscillate from one gain step to another. If a
potentiometer is used to adjust the voltage on the control terminals, the gain increases as the potentiometer is
turned in one direction and decreases as it is turned back the other direction. The trip point, where the gain
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