TPA1517_17 Datasheet, PDF (12/23 Pages) Texas Instruments – 6-W STEREO AUDIO POWER AMPLIFIER

TPA1517
SLOS162D – MARCH 1997 – REVISED FEBRUARY 2007
www.ti.com
APPLICATION INFORMATION (continued)
The audio outputs are biased to a midrail voltage which is shown by the following equation:
V_MID
+
V_CC
2
The audio inputs are always biased to 2.1 V when in mute or normal mode. Any dc offset between the input
signal source and the input terminal is amplified and can seriously degrade the performance of the amplifier. For
this reason, it is recommended that the inputs always be connected through a series capacitor (ac coupled). The
power outputs, also having a dc bias, must be connected to the speakers via series capacitors.
MUTE/STANDBY OPERATION
The TPA1517 has three modes of operation; normal, mute, and standby. They are controlled by the voltage on
the M/SB terminal as described in Figure 24. In normal mode, the TPA1517 amplifies the signal applied to the
two input terminals providing low impedance drive to speakers connected to the output terminals. In mute mode,
the amplifier retains all bias voltages and quiescent supply current levels but does not pass the input signal to
the output. In standby mode, the internal bias generators and power-drive stages are turned off, thereby
reducing the supply current levels.
22
NORMAL
9.3
Undetermined State
8.2
MUTE
3.5
Undetermined State
2
STANDBY
0
Figure 24. Standby, Mute, and Normal (On) Operating Conditions
The designer must take care to place the control voltages within the defined ranges for each desired mode,
whenever an external circuit is used to control the input voltage at the M/SB terminal. The undefined area can
cause unpredictable performance and should be avoided. As the control voltage moves through the undefined
areas, pop or click sounds may be heard in the speaker. Moving from mute to normal causes a very small click
sound. Whereas moving from standby to mute can cause a much larger pop sound. Figure 25 shows external
circuitry designed to help reduce transition pops when moving from standby mode to normal mode.
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