The MC642 is a pulse width modulation (PWM) fan speed controller for use with DC motors. It provides temperature proportional speed control. A thermistor connected to the VIN input furnishes the required control voltage of 1.25V to 2.65V for 0% to 100% PWM duty cycle. Minimum fan speed is set by a simple resistor divider on the VMIN input. An integrated Start–Up Timer ensures reliable motor start–up at turn–on, coming out of Shutdown Mode, or following a transient fault. A stalled, open, or unconnected fan causes the MC642 to trigger its start–up timer once. If the fault persists, the FAULT output goes low, and the device is latched in Shutdown Mode. Features include: Shutdown Mode for Power Saving, Supports Low Cost NTC/PTC Thermistors, Temperature Proportional Speed for Acoustic Control / Longer Fan Life, Fan Voltage Independent of MC642 Supply Voltage, Fault Detection Circuits Protect Against Fan Failure and Aid System Testing, Operating Temperature Range: 0°C to +85°C. Typical applications: Power Supplies, Personal Computers, UPS’s, Power Amplifiers, etc.
The MC642 is a pulse width modulation (PWM) fan speed controller designed for use with DC motors. It provides temperature proportional speed control using a thermistor connected to the VIN input to furnish a control voltage ranging from 1.25V to 2.65V, which corresponds to a 0% to 100% PWM duty cycle.
The device features an integrated Start-Up Timer that ensures reliable motor start-up at turn-on or when exiting Shutdown Mode. It includes fault detection circuits that trigger the FAULT output if a stalled, open, or unconnected fan is detected, latching the device in Shutdown Mode to prevent system damage.
| Operating Temperature Range | 0°C to +85°C |
|---|---|
| Supply Voltage (VDD) | 3.0V to 5.5V |
| PWM Frequency (typical) | 30 Hz |
| Control Voltage Range | 1.25V to 2.65V |
The SENSE input detects pulses from fan rotation chopping current through a sense resistor; the absence of pulses indicates a fault.
The MC642 enters Shutdown mode when the voltage on VIN is pulled below VSHDN.