3 Benefits of Y-Bridge

The Y-Bridge feature is particularly advantageous for systems requiring a high-voltage power stage supply, such as 2S–4S battery configurations (7V–14V). In Texas Instruments devices, this pin is typically referred to as PVDD. The PVDD supply can be sourced from an external power supply, an external boost circuit output, or generated internally from the VBAT using an integrated boost circuit, available in devices like the TAS2572, TAS2574, and TAS2120. The VDD rail, also represents the lower voltage supply already present in the system, typically 1.8V in the TAS2x20 and TAS257x device families. When the power stage supply (PVDD) is 5V or higher, switching between PVDD and the 1.8V rail offers greater benefits compared to scenarios where PVDD is less than 5V. Therefore, the Y-Bridge feature is most advantageous in systems that require a high-voltage output stage.

Additionally, the Y-Bridge feature dynamically selects between PVDD and VDD based on a predefined threshold. When the audio output signal exceeds a programmed threshold, the Class-D output switches to the high-voltage supply (PVDD). Below this threshold, the output continues using the 1.8V rail (VDD). This threshold is user-configurable, typically set around 100mW for most use cases. The efficiency plot illustrates the improved efficiency up to this threshold. Beyond this point, the efficiency typically aligns with that of a system without the Y-Bridge.

Figure 3-1 shows the functional block diagram of a smart amplifier with Y-Bridge feature