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General Purpose Motor Drivers in 3-15 Volt Range Slide 11

The LV8405V is a good choice for stepper motor control of zoom and focus in a video projector application. Video projectors in the mid to high-end use motors that are fairly large to drive the larger lens that they contain. In this case, higher torque is needed from the motor and high current capability is required for the motor driver. The package size of LV8405V is small but it incorporates two H-bridges with a maximum current capability of 1.4 A. Hence this device can support one stepper motor or two DC motors. Also with its low 0.75 on resistance, voltage loss during motor drive operation is low, thus generating less heat. The output transistor H-bridge is N channel-N channel. This means the gate voltage on the high side N channel FET is generated from an internal charge pump circuit, enabling low on resistance. Some motor drivers will use a P channel – N channel transistor configuration. The advantage it has is that no charge pump is necessary for the P channel FET to turn fully on. The disadvantage is that a P channel FET will require nearly four times as much die area to have the same RDS on as an N channel. The space required by the charge pump circuit is considerably less. In addition, the charge pump is able to fully turn on the FET over a wide input voltage range. Because of its wide tolerances, once a designer becomes familiar with this part, it will be used in many other motor driver applications.

PTM Published on: 2013-02-04