DS2746 Low-Cost 2-Wire Battery Monitor

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Figure 4. APPLICATION EXAMPLE

2.5V

(1)

10nF

DS2746

AIN0

VIN

VOUT

AIN1

SDA

VSS

SCL

Pack+

Pack-

System

Serial

Bus

(1) Optional for 8kV/15kV ESD

Protection IC

(Li+/Polymer)

1nF

1nF

Therm

PackID

System

VDD

System

VSS

SNS

VDD

(1) 5.6V

1K

CTG

1K

1K

150

POWER MODES

The DS2746 operates in one of two power modes: active and sleep. While in active mode, the DS2746 operates as

a high-precision battery monitor with voltage, auxiliary inputs, current and accumulated current measurements

acquired continuously and the resulting values updated in the measurement registers. Read and write access is

allowed to all registers. In sleep mode, the DS2746 operates in a low-power mode with no measurement activity.

The DS2746 operating mode transitions from SLEEP to ACTIVE when:

The DS2746 operating mode transitions from ACTIVE to SLEEP when:

CAUTION: If SMOD = 1, a pull-up resistor is required on SCL and SDA in order to ensure that the DS2746

transitions from SLEEP to ACTIVE mode when the battery is charged. If the bus is not pulled up, the DS2746

remains in SLEEP and cannot accumulate the charge current.

MEASUREMENT SEQUENCE

The DS2746 uses seperate A/D converters to make voltage and current measurements. Each A/D converter

operates completely independent of the other, allowing measurements of voltage and current to be made in

parallel. Current Measurements are made at a resolution of 13 bits plus sign bit. The current register is updated

every 878ms with the average for that time period.

All Voltage Measurements are made at a resolution of 11 bits plus sign bit. The DS2746 continouly cycles through