ANALOG HIGH POWER OUTPUT DRIVERS
SLAS497C – AUGUST 2006 – REVISED DECEMBER 2008 ............................................................................................................................................. www.ti.com
The TLV320AIC31 includes an output level control on each output driver with limited gain adjustment from 0 dB
to 9 dB. The output driver circuitry in this device are designed to provide a low distortion output while playing
full-scale stereo DAC signals at a 0-dB gain setting. However, a higher amplitude output can be obtained at the
cost of increased signal distortion at the output. This output level control allows the user to make this tradeoff
based on the requirements of the end equipment. Note that this output level control is not intended to be used as
a standard output volume control. It is expected to be used only sparingly for level setting, that is, adjustment of
the full-scale output range of the device.
Each differential line output driver can be powered down independently of the others when it is not needed in the
system. When placed into powerdown through register programming, the driver output pins will be placed into a
3-state, high-impedance state.
The TLV320AIC31 includes four high-power output drivers with extensive flexibility in their usage. These output
drivers are individually capable of driving 40 mW each into a 16-
load in single-ended configuration, and they
can be used in pairs to drive up to 500 mW into an 8-
load connected in bridge-terminated load (BTL)
configuration between two driver outputs.
The high-power output drivers can be configured in a variety of ways, including:
1. driving up to two fully differential output signals
2. driving up to four single-ended output signals
3. driving two single-ended output signals, with one or two of the remaining drivers driving a fixed VCM level,
for a pseudo-differential stereo output
4. driving one or two 8-
speakers connected BTL between pairs of driver output pins
5. driving stereo headphones in single-ended configuration with two drivers, while the remaining two drivers are
connected in BTL configuration to an 8-
speaker.
The output stage architecture leading to the high-power output drivers is shown in
Figure 31, with the volume
control and mixing blocks being effectively identical to that shown in
Figure 30. Note that each of these drivers
have a output level control block like those included with the line output drivers, allowing gain adjustment up to
+9 dB on the output signal. As in the previous case, this output level adjustment is not intended to be used as a
standard volume control, but instead is included for additional full-scale output signal level control.
Two of the output drivers, HPROUT and HPLOUT, include a direct connection path for the stereo DAC outputs to
be passed directly to the output drivers and bypass the analog volume controls and mixing networks, using the
DAC_L2/R2 path. As in the line output case, this functionality provides the highest quality DAC playback
performance with reduced power dissipation, but can only be utilized if the DAC output does not need to route to
multiple output drivers simultaneously, and if mixing of the DAC output with other analog signals is not needed.
This direct connection path will attenuate the signal by a factor of 1 dB.
36
Copyright 2006–2008, Texas Instruments Incorporated