Fan Controllers Offer PWM Speed Control

Dec. 1, 1999

The TC647 and TC649 are standalone, low-cost fan managers that integrate a PWM fan speed controller with start-up timer and fan fault detection circuits. The PWM fan speed control reduces acoustic noise of the fan, extends fan life, and lowers average fan operating current. The devices drive any standard two-wire fan through a low-cost transistor or logic level MOSFET. The devices take as input a temperature signal generated with a NTC thermistor and resistor. They provide temperature proportional fan speed control, increasing fan speed from 40% to 100% based on a user-programmed temperature range. The devices are different from the firm's TC642 and TC646 in that they do not include an over-temperature fault alert. The TC647 has a logic shutdown on Pin 3, and the TC649 performs a shutdown if a fault condition persists at Pin 5.

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