10.2.1 Stereo Bridge Tied Load Application

A stereo system generally refers to a system in which there are two full range speakers without a separate amplifier path for the speakers that reproduce the low-frequency content. In this system, two channels are presented to the amplifier via the digital input signal. These two channels are amplified and then sent to two separate speakers.

Most commonly, the two channels are a pair of signals called a stereo pair, with one channel containing the audio for the left channel and the other channel containing the audio for the right channel.

The Stereo BTL Configuration with Headphone and Line Driver Amplifier application is shown in Figure 68.

Figure 68. Stereo Bridge Tied Load Application

10.2.1.2 Detailed Design Procedure

10.2.1.2.1 Component Selection and Hardware Connections

The typical connections required for proper operation of the device can be found in the TAS5731EVM User’s Guide (SLOU331). The device was tested with this list of components; deviation from this list of typical application components, unless recommended by this document, may produce unwanted results, which could range from degradation of audio performance to destructive failure of the device.

10.2.1.2.2 I²C Pullup Resistors

Customary pullup resistors are required on the SCL and SDA signal lines. They are not shown in the Typical Application Circuits, because they are shared by all of the devices on the I²C bus and are considered to be part of the associated passive components for the System Processor. These resistor values must be chosen per the guidance provided in the I²C Specification.

10.2.1.2.3 Digital I/O Connectivity

The digital I/O lines of the TAS5731M are described in previous sections. As discussed, whenever a static digital pin (that is a pin that is hardwired to be HIGH or LOW) is required to be pulled HIGH, it must be connected to DVDD through a pullup resistor to control the slew rate of the voltage presented to the digital I/O pins. It is not, however, necessary to have a separate pullup resistor for each static digital I/O line. Instead, a single resistor can be used to tie all static I/O lines HIGH to reduce BOM count.

10.2.1.2.4 Recommended Start-Up and Shutdown Procedures

Figure 69. Recommended Command Sequence

Figure 70. Power-Loss Sequence

10.2.1.2.4.1 Initialization Sequence

	Use the following sequence to power up and initialize the device:
		1.	Hold all digital inputs low and ramp up AVDD/DVDD to at least 3 V.
		2.	Initialize digital inputs and PVDD supply as follows:
			•	Drive RESET = 0, PDN = 1, and other digital inputs to their desired state while ensuring that all are never more than 2.5 V above AVDD/DVDD. Wait at least 100 µs, drive RESET = 1, and wait at least another 13.5 ms.
			•	Ramp up PVDD to at least 8 V while ensuring that it remains below 6 V for at least 100 µs after AVDD/DVDD reaches 3 V. Then wait at least another 10 µs.
		3.	Trim oscillator (write 0x00 to register 0x1B) and wait at least 50 ms.
		4.	Configure the DAP via I2C, see TAS5731EVM Evaluation Module User's Guide (SLOU331) for typical values.
		5.	Configure remaining registers.
		6.	Exit shutdown (sequence defined inShutdown Sequence).

10.2.1.2.4.2 Normal Operation

	The following are the only events supported during normal operation:
		1.	Writes to master/channel volume registers
		2.	Writes to soft-mute register
		3.	Enter and exit shutdown (sequence defined in Shutdown Sequence)

NOTE

Event 3 is not supported for 240 ms + 1.3 × t_start after trim following AVDD/DVDD power-up ramp (where t_start is specified by register 0x1A).

10.2.1.2.4.3 Shutdown Sequence

	Enter:
		1.	Write 0x40 to register 0x05.
		2.	Wait at least 1 ms + 1.3 × tstop (where tstop is specified by register 0x1A).
		3.	If desired, reconfigure by returning to step 4 of initialization sequence.
	Exit:
		1.	Write 0x00 to register 0x05 (exit shutdown command may not be serviced for as much as 240 ms after trim following AVDD/DVDD power-up ramp).
		2.	Wait at least 1 ms + 1.3 × tstart (where tstart is specified by register 0x1A).
		3.	Proceed with normal operation.

10.2.1.2.4.4 Power-Down Sequence

	Use the following sequence to power down the device and its supplies:
		1.	If time permits, enter shutdown (sequence defined in Shutdown Sequence); else, in case of sudden power loss, assert PDN = 0 and wait at least 2 ms.
		2.	Assert RESET = 0.
		3.	Drive digital inputs low and ramp down PVDD supply as follows:
			•	Drive all digital inputs low after RESET has been low for at least 2 µs.
			•	Ramp down PVDD while ensuring that it remains above 8 V until RESET has been low for at least 2 µs.
		4.	Ramp down AVDD/DVDD while ensuring that it remains above 3 V until PVDD is below 6 V and that it is never more than 2.5 V below the digital inputs.

10.2.2 Mono Parallel Bridge Tied Load Application

A mono system refers to a system in which the amplifier is used to drive a single loudspeaker. Parallel Bridge Tied Load (PBTL) indicates that the two full-bridge channels of the device are placed in parallel and drive the loudspeaker simultaneously using an identical audio signal. The primary benefit of operating the TAS5731M device in PBTL operation is to reduce the power dissipation and increase the current sourcing capabilities of the amplifier output. In this mode of operation, the current limit of the audio amplifier is approximately doubled while the on-resistance is approximately halved.

The loudspeaker can be a full-range transducer or one that only reproduces the low-frequency content of an audio signal, as in the case of a powered subwoofer. Often in this use case, two stereo signals are mixed together and sent through a low-pass filter in order to create a single audio signal which contains the low frequency information of the two channels.

The Mono Parallel Bridge Tied Load application is shown in Figure 71.

Figure 71. Mono Parallel Bridge Tied Load Application

10.2.3 2.1 Application

A 2.1 system generally refers to a system in which there are two full range speakers with a separate amplifier path for the speakers which reproduce the low-frequency content. In this system, two channels are presented to the amplifier via the digital input signal, these are driven into two single-ended speakers and are mixed into a third channel, conditioned to stream low-frequency content into a differentially connected speaker.

The 2.1 application is shown in Figure 72.

Figure 72. Simplified 2.1 Application Diagram