1 Introduction

Audio amplifiers traditionally use a low-voltage rail (VDD) for I/Os and internal biasing, alongside a high-voltage supply (PVDD) for power stage switching and amplification. At low voltage levels of the output signals, when the power demand is low, the efficiency often falls below 20% due to unnecessary headroom from the single high-voltage supply.

To address this inefficiency, TI developed the remarkable Y-Bridge architecture. This design enables the amplifier to seamlessly switch between two power supplies based on the required power level, reducing idle power consumption by 90% and boosting efficiency by 15–20% at low power levels, all without compromising audio performance. Combined with TI’s industry-leading algorithms, this architecture helps original equipment manufacturers (OEM) to maximize efficiency and extend battery life of the OEM end products.

As shown in Figure 1-1, when Y-Bridge is being used, efficiency is significantly improved at low power (less than 100mW) over the traditional amplifiers with no Y-Bridge.