SLASEA5C March 2016 – May 2017 TAS5753MD
Audio amplifiers which incorporate switching output stages must have special attention paid to their layout and the layout of the supporting components used around them. The system level performance metrics, including thermal performance, electromagnetic compliance (EMC), device reliability, and audio performance are all affected by the device and supporting component layout. Ideally, the guidance provided in the Application Information section with regard to device and component selection can be followed by precise adherence to the layout guidance shown in . The examples represent exemplary baseline balance of the engineering trade-offs involved with laying out the device. The designs can be modified slightly as needed to meet the needs of a given application. For example, in some applications, solution size can be compromised to improve thermal performance through the use of additional contiguous copper near the device. Conversely, EMI performance can be prioritized over thermal performance by routing on internal traces and incorporating a via picket-fence and additional filtering components.
Placing the bypassing and decoupling capacitors close to supply has been long understood in the industry. The placement of the capacitors applies to AVDD and PVDD. However, the capacitors on the PVDD net for the TAS5753MD device deserve special attention. The small bypass capacitors on the PVDD lines of the DUT must be placed as close the PVDD pins as possible. Not only does placing these devices far away from the pins increase the electromagnetic interference in the system, but doing so can also negatively affect the reliability of the device. Placement of these components too far from the TAS5753MD device may cause ringing on the output pins that can cause the voltage on the output pin to exceed the maximum allowable ratings shown in the Absolute Maximum Ratings table, damaging the device. For that reason, the capacitors on the PVDD net must be no further away from their associated PVDD pins than what is shown in the example layouts in the Layout Examples section.
Follow the layout examples shown in the Layout Examples section of this document to achieve the best balance of solution size, thermal, audio, and electromagnetic performance. In some cases, deviation from this guidance may be required due to design constraints which cannot be avoided. In these instances, the system designer should ensure that the heat can get out of the device and into the ambient air surrounding the device. Fortunately, the heat created in the device naturally travels away from the device and into the lower temperature structures around the device.
Primarily, the goal of the PCB design is to minimize the thermal impedance in the path to those cooler structures. These tips should be followed to achieve that goal: