IC Keeps Variable Speed Fans And Blowers Under Tight Control

By integrating rotational speed sensing, locked rotor detection and automatic recovery functions, the ZXBM2000 series of controller ICs is said to deliver complete variable speed control of 2-phase DC brushless fan and blower motors rated up to 100W. The controller's 2-phase drive outputs deliver up to 80 mA to a pair of external MOSFETs or bipolar transistors connected to the fan motor windings. Speed control is achieved by applying a variable external voltage or a NTC thermistor input. And to detect fan rotor position, a built-in Hall amplifier enables the Hall sensor to be directly interfaced to the IC and so eliminates the need for external signal conditioning circuitry. Three variants of the chip are available to provide designers with a choice of diagnostic outputs: ZXBM2003 with a frequency generator (rotor speed) output; ZXBM2002 with a locked rotor error output; and ZXBM2001 for combining both signals on a dual function pin. When an obstruction in the fan blade, or a seized bearing causes the rotor to lock, the phase drive outputs go into a safe drive mode to protect the transistor pair and motor windings. The fan motor control IC in the ultra-small MSOP10 package costs $0.60 each/1,000. For additional information, call Neil Chadderton at ZETEX INC., Hauppauge, NY. (631) 360-2222.