DS2746 Просмотр технического описания (PDF) - Dallas Semiconductor -> Maxim Integrated

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DS2746

Low-Cost 2-Wire Battery Monitor with Ratiometric A/D Inputs

Dallas Semiconductor -> Maxim Integrated 

Figure 3. Block Diagram

DS2746 Low-Cost 2-Wire Battery Monitor

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

measure a thermistor or an ID resistor located inside the battery pack. The VOUT output provides the pullup voltage

for the resistor divider networks. The DS2746 disables VOUT after measuring the auxiliary inputs to reduce power

use by the measurement system. VOUT operation can be disabled through software to further reduce power

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

through the VIN, AIN0, and AIN1 pins repeatedly in that order. An internal reference is used to measure VIN voltage.

AIN0 and AIN1 are measured as a percentage of VOUT. This ratiometric measurement of the Auxiliary inputs

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.

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