Power Electronics

Data Points

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SiC to Grab Larger Share of Device Market

The silicon carbide (SiC) devices market is positioned for dramatic growth in the next six years, both economically and technologically, according to a report published in June by Yole Développement (Lyon, France), a market research and strategic consulting company.

According to the report, “PowerSiC 06: Status & Forecasts Silicon Carbide Devices for Power Electronics Market,” SiC Schottky diodes are offering sharp improvements over silicon-based diodes, resulting in the need for a complete redesign of the power supply. The report says that this has led to a slow market penetration, which started with high-end SiC devices and is now filtering down to middle-tier applications. The market for SiC Schottkys will reach about $45 million in 2010, the report forecasts, as the price of these components drops from approximately $0.45/A today to about $0.02/A in the future.

Yole Développement predicts that power factor correction (PFC) products will account for approximately $75 million of the SiC device market in 2012. Other applications for SiC components will include electric motor drives such as those used in hybrid electric vehicles and power converters used in solar and wind power generation. The market research firm notes that 5 million hybrid cars could benefit from SiC devices in 2016. For more information, see www.yole.fr/pagesAn/products/powersic.asp.

3-A Digital POL is Small and Easy to Use

Zilker Labs' ZL2105 is a 3-A buck converter that integrates full digital power-management capabilities. Housed in a 6-mm × 6-mm 36-lead QFN, the chip requires less than 2 cm2 of pc board space to complete a point-of-load converter (POL) design capable of stepping down a 4.5-V to 14-V input to a 0.6-V to 5.5-V output (see the figure). A key feature of the ZL2105 is its ease of use, which refers both to how simply the part may be configured or programmed,as well as its ability to interface seamlessly with the company's ZL2005 device.

Like its predecessor the ZL2005, the new device uses the company's Digital DC technology to provide digital controlled power management and power conversion with small size and high efficiency. As for the latter characteristic, the ZL2105 promises greater than 90% efficiency when converting a 12-V input to a 3.3-V output. But unlike the ZL2005, which relied on external MOSFETs to provide stepdown conversion at currents as high as 30 A per phase, the ZL2105 is a lower current, 3-A POL with power MOSFETs in package. The ZL2105 consists of two die co-packed in the QFN.

Because both parts use the same digital control architecture, the ZL2005 and Z2105 can be configured using either pin-strap connections or resistor selection, or via PMBus commands sent over the serial port. They offer a similar set of power-management capabilities including digital soft-start and soft-stop; precision delay and ramp up; voltage tracking, sequencing and monitoring; output voltage and current monitoring; and thermal monitor with shutdown. The ZL2105 specifies 1% output-voltage accuracy and the ability to switch at frequencies ranging from 200 kHz to 2 MHz.

To combine multiple Digital DC ICs in a given application without programming, the designer simply configures each IC via pin-strap selection and connects the serial bus (SMBus) of each device. The devices then communicate with each other via the SMBus and can operate independently of a host controller. The devices may be monitored and controlled individually or as a system.

According to Jim Templeton, Zilker Labs' vice president of marketing, the ability to operate without a host controller sets the Digital DC chips apart from other devices (ICs or modules) that perform power conversion and power management. “Customers can combine multiple Digital DC devices on a given PCB and easily configure the parts to simplify a complicated power design. Ours are the only solutions to offer this ‘plug and play’ experience for board-level power.”

Templeton also notes that the ZL2005 and ZL2105 are unique among power-conversion/power-management devices in that they don't require a separate regulated power supply. On-chip LDOs provide the power needed at startup.

Zilker Labs began sampling the ZL2105 in July to select customers. Pricing starts at $2.80 in quantities of 1000. An evaluation kit, the ZL2105EV1, is also available. For more information, see www.zilkerlabs.com.

Chip Enables Customized Fuel-Gauge Algorithms

Dallas Semiconductor's DS2790 is a programmable single-cell Li-ion fuel gauge and protector. With its integrated MAXQ microcontroller, extensive program and data memory, and accurate measurement system for battery current, voltage and temperature, the DS2790 provides a platform for customizing single-cell-battery, fuel-gauging algorithms.

According to the vendor, this chip overcomes the shortcomings of existing fuel-gauge ICs for single-cell Li-ion applications, which have lacked either sufficient on-chip memory or processing power. These deficiencies forced equipment manufacturers to adapt fuel-gauge ICs developed for 9-cell to 12-cell count battery packs, despite the high cost of those ICs.

At the heart of the DS2790's computing core is the low-power 16-bit MAXQ20 microcontroller with its accumulator-based (MAC), 16-bit RISC architecture. Highly efficient, its fetch and execution operations are completed in one cycle without pipelining because the instruction contains both the operation code and data. The processing core is supported by a 16-level hardware stack, which enables fast subroutine calling and task switching. Data can be quickly and efficiently manipulated with three internal data pointers. Multiple data pointers allow more than one function to access data memory without having to save and restore data pointers each time.

To allow the user to program proprietary algorithms, the DS2790 contains programming memory, data EEPROM and data RAM. The memory is arranged in a Harvard architecture, with separate address spaces for program and data memory. The 16 kbytes of programming memory consists of 8 kbytes of password-protected EEPROM and 8 kbytes of ROM. The inclusion of EEPROM allows the devices to be reprogrammed.

The ROM contains routines that allow reprogramming over the I2C interface, SHA-1 authentication and support for in-circuit debugging. The data EEPROM consists of 128 bytes, and is available for storing data such as charge parameters, cell characteristics,and manufacturing data that should remain unaffected by battery depletion, accidental shorts or ESD events. The data RAM is 512 bytes and is used for temporary data storage.

The DS2790 also provides precise current, accumulated current, voltage and temperature measurements. The 12-bit (plus a sign bit) current measurements are an average of 128 individual current samples. The current measurements are internally summed to produce the accumulated current with accuracy within ±2% of full-scale measurement, ±4 µV over a range of ±64 mV. Using a 15-mΩ sense resistor, this current accuracy translates to within ±2% of full-scale ±267 µA over a 4.2-A range. Standby currents are measured with an accuracy of ±195 µA.

The DS2790 measures voltage as a 10-bit (plus a sign bit) value over a 0-V to 4.75-V range with a resolution of 4.8 mV. An on-chip temperature sensor measures the temperature of the battery and reports the results as a 10-bit (plus a sign bit) value with a resolution of 0.125°C. All measured data and any password-protected reprogramming of the EEPROM memory can be communicated to the host through the DS2790's I2C communication interface.

The IC's Li-ion protection circuitry is comprised of an autonomous state machine that provides overvoltage, undervoltage, and over- and underdischarge protection. Safety and reliability are increased because the protection function does not rely on the CPU and, therefore, does not depend on its loading to perform other functions.

Available in 28-pin TSSOPs and TDFNs, the DS2790 is priced starting at $2.50 each in quantities of 1000. For a copy of the data sheet, see www.maxim-ic.com/DS2790.

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