System management microcontroller cuts power and cooling costs

Maxim Integrated Products introduces the MAX31782, a system management microcontroller that 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 highly precise zoned-cooling schemes. This approach minimizes 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 due to dust accumulation, and acoustic noise reduction.

A completely C-language programmable solution, the MAX31782 allows system designers to quickly and easily customize algorithms for precision zoned cooling in complex systems such as servers, network switches and routers, and base stations. With the ever-increasing demand for computing and storage capacity, data center energy efficiency has become an important public policy concern. The EPA estimates that data centers accounted for 1.5% of U.S. electricity consumption in 2006, and this demand is expected to nearly double by 2011, necessitating the development of an additional 10 power plants. Increasing data center energy efficiency can help avoid these 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. Indeed, many of today's data centers are unable to achieve maximum server density precisely 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 precision 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.

Because fan power consumption is approximately equal to a square of its speed, reducing fan speed by just 30% can cut power consumption by as much as 50% . These power savings can provide significant cost savings for end users, while reducing the environmental footprint of the data center as a whole. The conventional circuit for implementing zoned cooling requires a microcontroller and an external multichannel temperature sensor. Compared to this multichip approach, the MAX31782 consumes 55% less board space and reduces cost by at least 25%.

Moreover, Maxim's solution offers the added benefit of higher precision. It incorporates a 6-channel, 12-bit analog-to-digital converter (ADC) with a temperature-sensing analog front-end (AFE) that allows direct connection to thermal diodes. The AFE offers 0.125° C resolution, series resistance cancellation for the entire external diode circuit, and configurable ideality factor to deliver the highest 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 Maxim's high-accuracy DS7505. Based on the temperature information, the MAX31782 can control up to six cooling fans, each with an independent 16-bit PWM output and timer/tachometer input. It thus provides a complete closed-loop system for multiple fans, allowing accurate zoned cooling with minimum energy expended for fan power.

Based on a 16-bit MAXQ(R) RISC microcontroller core, the MAX31782 provides ample space for programs and data with 32-KWord reprogrammable flash and 1-KWord RAM for data storage. C-language and assembly-based programming is supported with the IAR Embedded Workbench(R) for MAXQ, available in time-limited or code-limited versions for free product evaluation. This tool also accommodates in-circuit flash programming and code debugging through the MAX31782's integrated JTAG-compatible debug port.

For more information, contact Maxim Integrated Products, 120 San Gabriel Dr., Sunnyvale, CA 94086. Phone: (408) 737-7600.

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