Monolithic Digital IC
For Polygonal Mirror Motors
Three-Phase Brushless Motor Driver

Overview
The LB11870 is a three-phase brushless motor driver developed for driving the motors used with the polygonal mirror in laser printers and plain paper copiers. It can implement, with a single IC chip, all the circuits required for polygonal mirror drive, including speed control and driver functions. The LB11870 can implement motor drive with minimal power loss due to its use of direct PWM drive.

Functions
• Three-phase bipolar drive
• Direct PWM drive
• Includes six high and low side diodes on chip.
• Output current control circuit
• PLL speed control circuit
• Phase lock detection output (with masking function)
• Includes current limiter, thermal protection, rotor constraint protection, and low-voltage protection circuits on chip.
• Deceleration type switching circuit (free running or reverse torque)
• PWM oscillator
• Power saving circuit