11.1.1 VDD Supply

The VDD supply required from the system is used to power several portions of the device. It provides power to internal regulators DVDD and AVDD that are used to power digital and analog sections of the device, respectively. Proper connection, routing, and decoupling techniques are highlighted in the TPA3244 Evaluation Module User's Guide (SLVUAT5) (as well as the Application Information section and Layout Examples section) and must be followed as closely as possible for proper operation and performance. Deviation from the guidance offered in the TPA3244 Evaluation Module User's Guide (SLVUAT5), which followed the same techniques as those shown in the Application Information section, may result in reduced performance, errant functionality, or even damage to the TPA3244 device. Some portions of the device also require a separate power supply which is a lower voltage than the VDD supply. To simplify the power supply requirements for the system, the TPA3244 device includes integrated low-dropout (LDO) linear regulators to create these supplies. These linear regulators are internally connected to the VDD supply and their outputs are presented on AVDD and DVDD pins, providing a connection point for an external bypass capacitors. It is important to note that the linear regulators integrated in the device have only been designed to support the current requirements of the internal circuitry, and should not be used to power any additional external circuitry. Additional loading on these pins could cause the voltage to sag and increase noise injection, which negatively affects the performance and operation of the device.

11.1.2 GVDD_X Supply

The GVDD_X supply required from the system is used to power the gate-drives for the output H-bridges. Proper connection, routing, and decoupling techniques are highlighted in the TPA3244 Evaluation Module User's Guide (SLVUAT5) (as well as the Application Information section and Layout Examples section) and must be followed as closely as possible for proper operation and performance. Deviation from the guidance offered in the TPA3244 device EVM User's Guide, which followed the same techniques as those shown in the Application Information section, may result in reduced performance, errant functionality, or even damage to the TPA3244 device.

11.1.3 PVDD Supply

The output stage of the amplifier drives the load using the PVDD supply. This is the power supply which provides the drive current to the load during playback. Proper connection, routing, and decoupling techniques are highlighted in the TPA3244 Evaluation Module User's Guide (SLVUAT5) (as well as the Application Information section and Layout Examples section) and must be followed as closely as possible for proper operation and performance. Due the high-voltage switching of the output stage, it is particularly important to properly decouple the output power stages in the manner described in the TPA3244 Evaluation Module User's Guide (SLVUAT5). The lack of proper decoupling, like that shown in the EVM User's Guide, can results in voltage spikes which can damage the device, or cause poor audio performance and device shutdown faults.

11.4.1 Thermal Performance

The TPA3244 device thermal performance is dependent on the thermal design of the PCB. As a result, the maximum continuous output power attainable will be influenced by the PCB design. The continuous power rating is lower than the peak output power capability of the device. The peak power rating of the TPA3244 deviceis based on the burst capability of the device. The peak to average power ratio of the TPA3244 device is well suited to handle even demanding audio playback without thermal shutdown. Thermal performance with typical audio content (burst) versus sine wave content (continuous) should be considered when defining the thermal test requirements for the end product.

11.4.2 Thermal Performance with Continuous Output Power

It is recommended to operate the TPA3244 device below the OTW threshold, which in most systems will require the average output power to be below the maximum peak output power. The maximum continuous power, the TPA3244 device will deliver depends directly on the thermal design of the PCB and for the entire system (closed box with no air flow, or a fanned system etc.). Thermal performance is also impacted by PVDD voltage and switching frequency. The best configuration for a given application will often depend on the continuous output power requirements.

11.4.3 Thermal Performance with Non-Continuous Output Power

As audio signals often have a peak to average ratio larger than one (average level below maximum peak output), the thermal performance for audio signals can be illustrated using burst signals with different burst ratios.

Figure 28. Example of audio signal

A burst signal is characterized by the high-level to low-level ratio as well as the duration of the high level and low level, e.g. a burst 1:4 stimuli is a single period of high level followed by 4 cycles of low level.

Figure 29. Example of 1:4 Burst Signal

The following analysis of thermal performance for the TPA3244 device is made with the TPA3244 EVM surrounded by still air (no airflow) with a controlled air temperature of 40°C. For 30 V operation the system is not thermally limited with 8Ω load, but depending on the burst stimuli for operation at 30V some thermal limitations may occur, depending on switching frequency and average to maximum power ratio. Low to maximum power ratio of the burst stimuli is given in the plots as for example P1:8 which equals low level burst cycles of 1/8 power of the high level cycles. The level of the high power cycles is set equal to 10% THD level.

PVDD = 30 V, fs = 450kHz

RL = 8Ω

TA = 40°C

Figure 30. Device and PCB Temperatures vs. Burst Ratio

PVDD = 26 V, fs = 450kHz

RL = 4Ω

TA = 40°C

Figure 32. Device and PCB Temperatures vs. Burst Ratio

PVDD = 30 V, fs = 600kHz

RL = 8Ω

TA = 40°C

Figure 31. Device and PCB Temperatures vs. Burst Ratio

PVDD = 26 V, fs = 600kHz

RL = 4Ω

TA = 40°C

Figure 33. Device and PCB Temperatures vs. Burst Ratio