DS2746 Low-Cost 2-Wire Battery Monitor

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Figure 2. Block Diagram

DETAILED DESCRIPTION

The DS2746 operates either in active mode where cell voltage, system current, and auxiliary inputs are monitored,

or in a low power sleep mode to conserve energy when the system is idle. While in active mode, the DS2746

contantly measures current flow through an external sense resistor. Each current measurement is reported with

sign and magnitude in a two-byte Current register. Offset bias and offset blanking features remove offset error from

the current A/D to improve measurement accuracy. Each current measurement is integrated into the Accumulated

Current register (ACR) to maintain a sum of all charge entering and exiting the cell.

The DS2746 has two auxiliary inputs to allow voltage sampling of resistor divider circuits. These can be used to

consumption when the auxiliary inputs are not in use.

A dedicated voltage A/D measures voltage of the cell and the auxiliary inputs. A mux on the input to the A/D cycles

prevents noise in the supply from affecting accuracy of the readings

The DS2746 measurements can be used directly to provide accurate fuel gauging in typical use conditions, or

along with FuelPack™ algorithms to form a complete and accurate solution for estimating remaining capacity over

wide temperature and operating conditions.

Through its 2-Wire interface, the DS2746 allows a host system read/write access to the Status/Configuration

register and Measurement registers. If sleep mode operation is enabled, holding both interface lines low forces the

DS2746 into a low power sleep mode where A/D measurements are paused and the ACR register is maintained.

FuelPack is a trademark of Dallas Semiconductor.