4 Power Threshold for Y Bridge

The level of power where the Y bridge switches from one supply to the other can be programmed by user in to designated registers. LVS threshold is set based on the output signal level and is measured in dBFS.

The LVS threshold can be set as an absolute value with respect to maximum output level or as a relative value with respect to VBAT1S supply.

It is important to know the switching between two supplies does not produce any audio artifact (pop, and so on).

ICs with Y-bridge function, such as TAS2780 and TAS2764, monitor the absolute value of audio signal.

The LVS threshold voltage is set by Low Voltage Signaling (LVS) registers. If the signal level drops below this threshold for longer than the hysteresis time, then the Class-D supply will switch to VBAT1S. The hysteresis time can be also programed in to designated registers. As shown in Figure 4-1, the open-drain BYP_EN pin will be de-asserted (actively pulling the output low) after a delay programmed and thus the Y Bridge will switch from VBAT1S to PVDD after a programmed delay. The LVS threshold can alternately be configured to be a value relative to the VBAT1S voltage.