L6235 three phase brushless DC motor driver.pdf

AN1625 APPLICATION NOTE L6235 THREE PHASE BRUSHLESS DC MOTOR DRIVER by Vincenzo Marano Modern motion control applications need more flexibility that can be addressed only with specialized ICs products. The L6235 is a fully integrated motor driver IC specifically developed to drive a wide range of BLDC motors with Hall effect sensors. This IC is a one-chip cost effective solution that includes several unique circuit design features. These features, including a universal decoding logic that allows the device to be used with most common Hall effect spacing, will be described. The principal aim of this development project was to produce an easy to use, fully protected power IC. In addition several key functions as protection circuit and high speed PWM current control allow to drastically reduce the external components count to meet requirements for many different applications. 1 INTRODUCTION For small-motor applications many appliance designers favor modern three phase brushless DC motors be- cause of the high efficiency (as great as 95%) and small size for a given delivered power. Designers have to handle control logic, torque and speed control, power-delivery issues and ensure safe operation in every load condition. The L6235 is a highly integrated, mixed-signal power IC that allows to easily design a complete motor control system for BLDC motor. Figure 1 shows the L6235 block diagram. The IC integrates six Power DMOS, a centralized logic circuit to decode hall effect sensors and a constant tOFF PWM current control technique (Syn- ch