Piezoelectric motors are used in digital cameras for autofocus, zooming and optical image stabilization. They are relatively small, lightweight and efficient, but they also require a complicated driving scheme. Traditionally, this challenge has been met with the use of separate circuits, including a step-up converter and an oversized generic full-bridge drive IC. The resulting high component count and large board space are especially problematic in the design of cameras for ever shrinking cell phones. The LT®3572 solves these problems by combining a step-up regulator and a dual full-bridge driver in a 4mm ×4mm QFN package. Figure 1 shows a typical LT3572 Piezo motor drive circuit. A step-up converter is used to generate 30V from a low voltage power source such as a Li-Ion battery or any input power source within the part’s wide input voltage range of 2.7V to 10V. The high output voltage of the step-up converter, adjustable up to 40V, is available for the drivers at the VOUT pin. The drivers operate in a full-bridge fashion, where the OUTA and OUTB pins are the same polarity as the PWMA and PWMB pins, respectively, and the OUTA and OUTB pins are inverted from PWMA and PWMB, respectively. The step-up converter and both Piezo drivers have their own shutdown control. Figure 2 shows a typical layout .
Tiny Dual Full-Bridge Piezo Motor Driver Operates from.pdf
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