BOS1901 basics

The BOS1901 is a single-chip piezo actuator driver with energy recovery, based on a patented CapDrive™ technology. It can drive actuators with up to 190 Vpp waveforms while operating from a 3 to 5.5 V supply voltage. Low power and small size make it ideal for a variety of applications requiring minimal power consumption and heat dissipation.

The 190 Vpp is achieved by alternating the voltage on the piezoelectric actuator from +95 V to -95 V.

When outputting +95 V, BOS1901 is in positive polarity. Pin OUT+ is set to VDD+95 V while pin OUT- is set to VDD. Thus the voltage difference seen by the actuator is +95 V.

When outputting -95 V, BOS1901 is in negative polarity. Pin OUT+ is set to VDD while pin OUT- is set to VDD+95 V. Thus the voltage difference seen by the actuator is -95 V.

In all situations, voltage on OUT+ and OUT- is driven between VDD and VDD+95 V. This means both piezo terminals are above the ground and considered active.

The figures below show how OUT+ and OUT- are behaving when the programmed voltage is positive (left) and negative (right). In both cases, both OUT+ and OUT- output a positive voltage. It is the voltage difference between both terminals that changes polarity.

Figure 1 OUT+ and OUT- voltage level when programming a positive (left) and a negative (right) voltage