SLAAEU5A June   2025  – September 2025 TAS2780 , TAS2781

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1 Introduction
  5. 2 What is Y-Bridge
  6. 3 Class-D Switching Modes and Register Settings
  7. 4 PWR_MODE1 [CDS_MODE = 00]
  8. 5 PWR_MODE2 [CDS_MODE = 11]
  9. 6 External Component Requirements
  10. 7 Benefits of Y-Bridge
  11. 8 Summary
  12. 9 References
  13. 10Revision History

2 What is Y-Bridge

As the name implies, the Y-Bridge power architecture resembles a “Y” configuration, in contrast to the conventional linear half-bridge topology. In a traditional half-bridge Class-D amplifier, the output stage operates solely from a single high-voltage supply rail (PVDD), regardless of the output power requirement. This results in substantial efficiency losses during low-power or idle conditions, where the full voltage headroom is unnecessary. The Y-Bridge architecture addresses this limitation by incorporating both a high-voltage rail (PVDDH) and a low-voltage rail (PVDDL) into the output stage.

At low output power levels, including idle states, the amplifier operates from the lower voltage rail (PVDDL), as the required headroom is minimal and can be met without risking signal clipping. This approach significantly improves power efficiency at lower output levels. When higher output power is demanded, the amplifier seamlessly transitions to the high-voltage rail (PVDDH), delivering the necessary headroom without compromising performance. In this state, the system’s efficiency aligns with that of a traditional Class-D amplifier. As a result, the Y-Bridge architecture delivers the most notable efficiency gains at low to moderate output levels—where conventional amplifiers typically operate least efficiently.

Figure 2-1 illustrates the structural and operational differences between a traditional Class-D amplifier and one utilizing the Y-Bridge architecture.

Traditional Class-D Amplifier vs Simplified Y-Bridge Architecture Figure 2-1 Traditional Class-D Amplifier vs Simplified Y-Bridge Architecture

Texas Instruments' latest audio amplifiers, the TAS2781 and TAS2783, incorporate the Y-Bridge architecture to enhance power efficiency during audio playback. Figure 2-2 shows the functional block diagram of the TAS278x device. The Y-Bridge feature can be enabled or disabled through device configuration, providing flexibility based on system requirements. Additionally, the amplifiers can be set to operate exclusively from either the low-voltage rail (PVDDL) or the high-voltage rail (PVDDH), depending on the desired performance characteristics. When configured to use only PVDDL or PVDDH, this is critical to make sure that the selected supply voltage is sufficient to avoid output clipping, particularly under higher output demands. Detailed description on these configurations and the operational implications is provided in Section 3.

Functional Block Diagram of TAS278x with Y-Bridge Feature Figure 2-2 Functional Block Diagram of TAS278x with Y-Bridge Feature