Chips Attack Barriers to Digital Control

Sep 1, 2008 12:00 PM
By David Morrison, Editor in Chief

Server and Gaming Applications

CHiL Semiconductor has announced two digital multi-phase buck controllers for VR11.1-compliant server and gaming/enthusiast desktop PC applications. Described as the first digital controllers to offer up to eight-phase control, the CHL8316 and CHL8318 controllers use a number of innovative digital-control techniques to achieve more than 90% efficiency across virtually all load ranges, according to the company. To support these controllers, the CHL8510 high-frequency MOSFET gate driver is also being introduced.

“By optimizing our architecture for fast transient response and coupling that capability with up to eight-phase control and several new innovative digital-control techniques, the CHL8316 and CHL8318 controllers offer data center managers and gaming/enthusiast desktop users unprecedented advantages in terms of power efficiency, performance and thermal management,” says Larry Spaziani, vice president of marketing for CHiL.

Many users are beginning to monitor efficiency at the system level. Data center managers can now track server power savings from virtualization or other conservation techniques on a control panel while energy-conscious individuals can visualize power savings on their desktop monitors. CHiL's products provide detailed, accurate SMBus power, current and efficiency information needed for users to easily manage energy-saving efforts.

The CHL8316 is an Intel VR11.1-compliant digital multiphase buck controller that supports up to six programmable interleaved synchronous buck phases. Using a graphical user interface, designers can digitally configure the switching frequency of each phase from 200 kHz to 1 MHz, as well as configure other device settings. The settings are then stored in nonvolatile memory embedded on chip.

To address the fast transients in today's VR11.1-compliant CPU designs, the CHL8316 incorporates an optimized ADC that responds to a very fast transient of >2000 A/µs, reducing capacitance and saving board space and component cost.

By digitally controlling current across six programmable synchronous phases, designers can use the CHL8316 to optimize power efficiency at high load conditions. As current drops, the CHL8316 automatically detects and dynamically reduces the number of phases to further improve power efficiency. A variable gate drive reduces MOSFET gate losses and improves efficiency at lower operating currents. Finally, these products report the operating voltage, current and efficiency through an SMBus, allowing system-level control of power management.

“At currents ranging from 30 A to 40 A, we simultaneously meet transient-control requirements and increase server power efficiency by about 8%. This results in a 150-W reduction at the voltage regulator [VR] level alone on a typically configured blade server,” says Ram Sudireddy, founder, president and CEO of CHiL Semiconductor.

To manage heat dissipation, the CHL8316 adds an external temperature sensor. In addition, a VR HOT function communicates heat levels to the CPU and an overtemperature-protection (OTP) circuit automatically shuts down VR PWM signals when the operating temperature exceeds a second threshold. The CHL8316 also features a current-balancing algorithm that automatically balances current across the IC's six phases during both dc and transient operation, to optimize thermal management.

The CHL8318 adds several capabilities to support higher-performance server and gaming/enthusiast desktop applications. Eight-phase control offers faster transient response and better power efficiency. Custom digital overclocking features allow users to extend the voltage range up to 2.3 V, while VID scaling and offset controls and load-line adjustment features offer additional performance enhancements. Importantly, none of the gaming features require additional external components.

The CHL8318 features the same power-efficiency capabilities found on the CHL8316. Using eight-phase control for high load conditions, along with dynamic phase control and adjustable gate drive for mid-to-low load conditions, designers can achieve better than 90% power efficiency across virtually all load conditions with the CHL8318.

To control the large amounts of heat generated by its overclocking functions, the CHL8318 also adds advanced thermal-management capabilities. Three external temperature sensors support more comprehensive monitoring and control of phase current to balance temperature variations. In addition, the controller adds the same programmable VR HOT and OTP features and the automatic thermal balancing capability as on the CHL8316.

To support the rapid development of VR solutions, the CHL8510 driver IC is designed to support these new buck controllers. The driver offers fast tri-level disable for the power status indicator signal in VR11.1 designs and LVCC down to 5 V for variable gate-drive functions.

In 1000-piece quantities, the six-phase CHL8316 controller is available in a 48-pin QFN and is priced at $2.49 each; the eight-phase CHL8318 controller is available in a 56-pin QFN and is priced at $3.29 each; and the CHL8510 MOSFET driver comes in a 10-pin DFN and sells for $0.49 each. All three devices are specified across the 0°C to 85°C range.

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