Dallas—Designed for especially cost-sensitive applications, Dallas Semiconductor's DS2745 is a Li+ battery monitor with an I2C interface that costs under $1. Mounted on either the host side or the battery-pack side of the application to continuously monitor battery capacity, the DS2745 measures current, accumulated current, voltage, and temperature.
The chip, monitoring the voltage drop across an external sense resistor, performs 16-bit bidirectional current measurement over a dynamic range of ±51.2mV with a resolution of 1.56 microvolts. With a 15-milliohm sense resistor, the current-sense range is ±3.4 amps with a (1 LSB) resolution of 104 microamps. Current values are accumulated with each measurement to support coulomb counting.
The chip measures battery voltage through a dedicated
voltage-sense input; results are stored in a two-byte
register with 11-bit (4.88 mV) resolution. On-chip
temperature measurements are stored in a two-byte register with a resolution of 0.125°C.
The I2C interface with software-programmable address gives the controlling microprocessor access to all data and status registers in the DS2745. A preliminary datasheet for this product is available at www.maxim-ic.com/DS2745. The device, in an 8-pin microMAX package, is priced at 98 cents each in 100k pieces.
Dallas Semiconductor, 1-800-998-8800, www.maxim-ic.com