Microcontroller enables precise zoned cooling

The Max31782 microcontroller combines six temperature measurement channels with six channels of closed-loop fan control.

By monitoring multiple temperature points throughout the system, the Max31782 enables enterprise system designers to implement precise zoned-cooling schemes.

This approach minimises system power consumption and cooling costs by individually adjusting the speed of each fan to deliver the exact amount of cooling required by each zone.

Added benefits of this technique include increased reliability through reduced fan wear, compensation for fan speed variances owing to dust accumulation and acoustic noise reduction.

A completely C-language programmable system, the Max31782 also enables designers to customise algorithms for precise zoned cooling in complex systems such as network switches and routers and base stations.

With the ever-increasing demand for computing and storage capacity, data centre energy efficiency has become an important public policy concern.

Increasing data centre energy efficiency can help avoid infrastructural costs, while offering end users significant savings on their electricity bills.

Much of the energy consumed by enterprise equipment is dissipated as heat.

This poses significant thermal management challenges, even more so with the high power densities afforded by blade servers.

Many of today's data centres are unable to precisely achieve maximum server density because they cannot manage the heat generated by these dense rack-mounted systems.

The problem with many systems is that they rely on imprecise thermal monitoring and, in turn, run their fans much faster than is necessary for optimal thermal performance.

By monitoring multiple temperature nodes across the system, enterprise system designers can use a multichannel fan-controller IC to implement precise zoned cooling.

This approach saves power by dynamically adjusting the speed of each cooling fan to meet the constantly changing thermal requirements of each zone.

As fan power consumption is approximately equal to a square of its speed, reducing fan speed by just 30 per cent can cut power consumption by as much as 50 per cent.

These power savings can provide cost savings for end users while reducing the environmental footprint of the data centre as a whole.

The conventional circuit for implementing zoned cooling requires a microcontroller and an external multichannel temperature sensor.

Compared with this multichip approach, the Max31782 consumes 55 per cent less board space and reduces cost by at least 25 per cent, according to the company.

In addition, Maxim's solution offers the added benefit of higher precision.

It incorporates a six-channel, 12-bit analogue-to-digital converter (ADC) with a temperature-sensing analogue front-end (AFE) that enables direct connection to thermal diodes.

The AFE offers 0.125C resolution, series-resistance cancellation for the entire external diode circuit and a configurable ideality factor to deliver high-temperature measurement accuracy.

The Max31782 can be directly connected to up to six remote thermal diodes, which are typically integrated on CPU, FPGA and ASIC ICs.

Using the on-chip master I2C interface, additional temperature points can be monitored with external digital temperature ICs, such as the company's DS7505.

Based on temperature information, the Max31782 can control up to six cooling fans, each with an independent 16-bit pulse-width-modulation (PWM) output and timer/tachometer input.

It therefore provides a complete closed-loop system for multiple fans, allowing accurate zoned cooling with minimum energy expended for fan power.