Power Electronics
Data Points

Data Points

Gas Gauge Technology Extends Battery Runtime

As use of Li-ion batteries expands into new applications, concern continues over the measurement of battery capacity, commonly called fuel or gas gauging. As equipment designers seek to maximize battery runtime, they face difficulties such as the inability to obtain accurate battery capacity measurements over the life of the battery pack. Other problems include the delay in displaying the battery's state of charge and the development effort required to implement fuel gauging.

Impedance Track gas gauge technology from Texas Instruments (TI) aims to eliminate these problems. It calculates remaining capacity in Li-ion battery packs with up to 99% accuracy throughout the life of a battery.

Impedance Track precisely gauges changes in impedance or resistance caused by battery age, temperature and cycle patterns, to predict runtime of 2-, 3- and 4-cell battery packs.

The technology supports other battery chemistries such as NiMH or NiCD. TI also plans to target single-cell Li-Ion powered applications.

The Impedance Track technology, which sits inside TI's Flash-based bq20z8x gas gauge chipset, analyzes precise state of charge when a battery pack is in a relaxed state by correlating between a battery pack's open circuit voltage and the current state of charge and temperature.

An exact “starting position” is determined for instant state of charge and total capacity is calculated from the amount of capacity that exists — eliminating the need for a full charge and discharge cycle. For applications such as heart defibrillators, which never fully charge and discharge, Impedance Track ensures instant and accurate capacity information.

Impedance Track's dynamic modeling algorithm determines how much a battery has degraded through age, temperature or usage, and then correlates typical chemical properties of the anode/cathode system in the battery's cell — no matter what brand of battery cell is used. Impedance Track even allows for the mixing of different manufacturers' cells in a single pack.

Many of today's gas gauge IC technologies depend on static and unreliable modeling techniques that require the creation of large databases to measure each attribute of hundreds of available battery parameters. TI's technology reduces development and implementation setup time required by original equipment designers and manufacturers to ensure proper characterization because those databases are no longer necessary.

The 2-chip bq20z8x gas gauge reports capacity information to the system host controller over an SMBus interface. A host controller manages remaining battery power to extend system runtime. The bq20z8x chipset also features TI's protection analog front-end (AFE) chip, the bq29312, with integrated 3.3-V, 25-mA LDO regulator.

Offered in 38-pin TSSOPs, the bq20z8x gas gauge chipset is sampling now, with volume production set for Q4. The bq29312 comes in a 24-pin TSSOP. Unit pricing in 1000-piece quantities is $4.35 for the bq20z8x and $1.20 for the bq29312.

For details, see power.ti.com.

PoE Midspan Market Forecast to Grow Rapidly

According to a report by Venture Development Corp. (VDC), “Power Over Ethernet: A Global Market Demand Analysis,” the worldwide market for Power-over-Ethernet (PoE) midspan solutions is forecast to steadily rise, doubling the number of PoE-enabled ports shipped each year between 2003 to 2007.

The forecast for worldwide shipment of midspan ports ranges from 1.1 million ports in 2003 to 3.1 million ports in 2005 to 8.1 million ports in 2007.

According to VDC, “Our latest research forecasts the compound annual growth rate (CAGR) for midspans to be an impressive 64% between 2003 and 2007. However, we also estimate that per port revenue will decline by more than 50%.”

For details, see www.vdc-corp.com.

Isolated Power Module

Vicor's V048K015T100 Voltage Transformation Module (VTM) delivers 100 A of output at voltages up to 1.5 V or 150 W at outputs up to 1.6 V, while operating from an input range of 26 Vdc to 55 Vdc. This high current and power capability is achieved using a V•I Chip BGA package that occupies less than 0.25 in.3, which results in a current density of 400-A/in.3 for the 1.5-V VTM.

The module achieves an efficiency of 90% at 1.2 V and 100 A, and better than 92% at 50 A. The VTM may be paralleled to deliver hundreds of amps at an output voltage settable from 0.8 Vdc to 1.6 Vdc.

The VTM can be operated open or closed loop. In open loop, the output voltage tracks its input voltage with a transformation ratio, K=1/32, and an output resistance, ROUT =1.0 mΩ. Closing the loop back to an input Pre-Regulator Module or dc-dc converter compensates for ROUT.

For more information, visit www.vicorpower.com.

PoE Power-Supply IC

Maxim Integrated Products' MAX5074 is a pulse-width-modulation (PWM) power IC with integrated power MOSFETs. It is targeted at isolated power supplies for IEEE 802.3af-compliant, Power-over-Ethernet (PoE) powered devices. The MAX5074 is suitable for converting -48 V to 3.3 V in power-sourcing equipment, which includes switch/routers and midspans. It can be used in flyback- and forward-converter isolated power supplies with a ±11 V to ±76 V input-voltage range and up to 15-W output power.

The MAX5074 provides a “look ahead” signal for driving secondary-side synchronous rectifiers, allowing greater than 90% efficiency without complicated drive schemes and additional discrete components. Other features include thermal shutdown, continuous short-circuit protection with hiccup-mode current limit, and a switching frequency that is resistor-/capacitor-programmable up to 500 kHz.

For more information, visit www.maxim-ic.com.

IC Charges 1- and 2-cell Li-ion Batteries

The MCP73861/2 from Microchip Technology are single- and dual-cell fully integrated Li-ion/Li-polymer charge management controllers that feature 0.5% voltage regulation accuracy. These linear chargers also offer on-board thermal regulation to optimize charge rate and charge cycle time based on operating conditions. Meanwhile, on-chip safety timers and thermal monitor provide time- and temperature-based charge termination.

Input voltage range is specified as 4.5 V to 12 V for the MCP73861 single-cell charger and 8.7 V to 12 V for the MCP73862 dual-cell charger. Offered in 4-mm × 4-mm QFNs, the MCP73861/2 are priced at $1.45 and $1.64 each, respectively, in quantities of 1000.

For more information, visit www.microchip.com

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