The TLV320AIC3104-Q1 includes four high-power output drivers with extensive flexibility in their usage. These output drivers are individually capable of driving 30 mW each into a 16-Ω load in single-ended configuration, and they can be used in pairs 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

The output stage architecture leading to the high-power output drivers is shown in Figure 7-7, with the volume control and mixing blocks being effectively identical to those shown in Figure 7-6. Note that each of these drivers has an 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 theDAC_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 used if the DAC is not being routed to multiple output drivers simultaneously, and if mixing of the DAC output with other analog signals is not needed.

Figure 7-7 Architecture of Output Stage Leading to High-Power Output Drivers

The high-power output drivers include additional circuitry to avoid artifacts on the audio output during power-on and power-off transient conditions. The user should first program the type of output configuration being used in page 0, register 14, to allow the device to select the optimal power-up scheme to avoid output artifacts. The power-up delay time for the high-power output drivers is also programmable over a wide range of time delays, from instantaneous up to 4 s, using page 0, register 42.

When these output drivers are powered down, they can be placed into a variety of output conditions based on register programming. If lowest-power operation is desired, then the outputs can be placed into a high-impedance state, and all power to the output stage is removed. However, this generally results in the output nodes drifting to rest near the upper or lower analog supply, due to small leakage currents at the pins. This then results in a longer delay requirement to avoid output artifacts during driver power on. In order to reduce this required power-on delay, the TLV320AIC3104-Q1 includes an option for the output pins of the drivers to be weakly driven to the VCM level they would normally rest at when powered with no signal applied. This output VCM level is determined by an internal band-gap voltage reference, and thus results in extra power dissipation when the drivers are in power down. However, this option provides the fastest method for transitioning the drivers from power down to full-power operation without any output artifact introduced.

The device includes a further option that falls between the other two—although it requires less power drawn while the output drivers are in power down, it also takes a slightly longer delay to power up without artifact than if the band-gap reference is kept alive. In this alternate mode, the powered-down output driver pin is weakly drive nto a voltage of approximately half the DRVDD1/2 supply level using an internal voltage divider. This voltage does not match the actual VCM of a fully powered driver, but due to the output voltage being close to its final value, a much shorter power-up delay time setting can be used and still avoid any audible output artifacts. These output voltage options are controlled in page 0, register 42.

The high-power output drivers can also be programmed to power up first with the output level (gain) control in a highly attenuated state; then the output driver automatically reduces the output attenuation slowly to reach the programmed output gain. This capability is enabled by default but can be enabled in page 0, register 40.