Overview
The LB11850VA is a single-phase bipolar fan motor driver with speed control function that works with a speed feedback signal. A highly efficient, quiet and low power consumption motor driver circuit, with a high speed accuracy and large variable speed can be implemented by adding a small number of external components.
This pre-driver is optimal for driving large scale fan motors (with large air volume and large current) such as those used in servers and consumer products.

Functions and Features
• Pre-driver for Single-phase Full-wave Drive
    ♦ PMOS-NMOS is Used as an External Power TR, Enabling High-efficiency and Low-power-consumption Drive by Means of the Low-saturation Output and Single-phase Full-wave Drive
• On-chip Speed Control Circuit
    ♦ The Speed Control (Closed Loop Control) Using a Speed Feedback Signal Makes it Possible to Achieve Higher Speed Accuracy and Lower Speed Fluctuations when Supply Voltage Fluctuates or Load Fluctuates, Compared with an Open-loop Control System. Separately Excited Upper Direct PWM Control Method is Used as the Variable-speed Control System
• External PWM Input or Analog Voltage Input Enabling Variable Speed Control
    ♦ The Speed Control Input Signal is Compatible with PWM Duty Ratio or Analog Voltages
• On-chip Soft Start Circuit
• Lowest Speed Setting Pin
    ♦ The Lowest Speed can be Set with the External Resistor
• Current Limiter Circuit Incorporated
    ♦ Chopper Type Current Limit at Start or Lock
• Reactive Current Cut Circuit Incorporated
    ♦ Reactive Current before Phase Change is Cut to Enable Silent and Low-consumption Drive
• Constraint Protection and Automatic Reset Functions Incorporated
• FG (Speed Detection), RD (Lock Detection) Output
• Constant-voltage Output Pin for Hall Bias