6-Channel PWM-Output Fan RPM Controller

The MAX31790 controls the speeds of up to six fans using six independent PWM outputs. The desired fan speeds (or PWM duty cycles) are written through the I²C interface. The outputs drive "4-wire" fans directly, or can be used to modulate the fan's power terminals using an external pass transistor.

Tachometer inputs monitor fan tachometer logic outputs for precise (±1%) monitoring and control of fan RPM as well as detection of fan failure. Six pins are dedicated tachometer inputs. Any of the six PWM outputs can also be configured to serve as tachometer inputs.

The PWMSTART inputs select the PWM output status at startup to ensure appropriate fan drive when power is first applied.

To ensure low acoustic impact of fan control, all changes in PWM duty cycle take place at a controlled, programmable rate.

The MAX31790's 3.0V to 5.5V supply voltage range and I²C-compatible interface make it ideal for fan control in a wide range of cooling applications. The MAX31790 is available in a 28-pin TQFN package and operates over the -40°C to +125°C temperature range.

Applications

* Networking * Servers * Telecom

* Provides Precise Fan Control and Monitoring for Large Fan Count Applications

* Controls Up to Six Independent Fans with PWM Drive

* Up to 12 Tachometer Inputs

* Controlled Duty Cycle Rate-of-Change for Best Acoustics

* Improves System Reliability

* Versatile Startup Configurations Provide Reliable Fan Control at Power-up without Having to Wait for System µC Direction

* I2C Bus Interface with Timeout and Watchdog