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I2C Battery Gas Gauges for Single Li-Ion Cells Offers 1% Accuracy

2nd March 2010

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Linear Technology Corporation introduces the LTC2941/LTC2942 battery gas gauges with an I2C interface for 2.7V to 5.5V systems. Unlike most coulomb counters that infer charge by sampling the current and integrating digitally, the LTC2941/LTC2942 use a continuous-time analog integrator to measure charge directly, resulting in minimal offset and gain error and better overall charge accuracy. The LTC2941 measures the charge flowing in and out of a battery to within 1% accuracy at room temperature. The LTC2942 does the same while also incorporating a 14-bit No Latency Δ∑ ADC to measure battery voltage and die temperature to within 1.3% and ±5°C accuracy, respectively.

/> The LTC2941 and LTC2942 are best suited for single-cell Li-Ion applications, including cell phones, cameras, MP3 players, and GPS receivers. Battery current is measured by monitoring the voltage across an external sense resistor and integrating this information to infer charge. A bidirectional analog integrator accommodates either current polarity (battery charge or discharge), and a programmable prescaler allows for a wide range of battery capacities. Charge, voltage*, and temperature* information are communicated to the host system over an I2C/SMBus compatible 2-wire interface that is also used to configure the gas gauge. The host can program high and low thresholds for all measured parameters, which if tripped, signal an alert using either the SMBus Alert protocol or by setting a register flag.

The LTC2941 and LTC2942 are offered in commercial and industrial versions, supporting operating temperature ranges from 0°C to 70°C and -40°C to 85°C, respectively. All devices are available today in a small RoHS compliant, 6-pin 2mm x 3mm DFN package. Pricing starts at $1.30 each for the LTC2941 and $1.50 each for the LTC2942, each in 1,000 piece quantities. Please visit www.linear.com for more product selection and information.

*LTC2942