DS2746 Просмотр технического описания (PDF) - Maxim Integrated

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DS2746

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

Maxim Integrated 

Figure 4. APPLICATION EXAMPLE

DS2746 Low-Cost 2-Wire Battery Monitor

Protection IC

(Li+/Polymer)

1nF

1nF

Pack+

150

1K

PackID

Therm

Pack-

VOUT

VIN

VDD

(1) 5.6V 10nF

AIN0

1K

SDA

AIN1

SCL

1K

VSS

SNS

CTG

DS2746

RSNS

(1) Optional for 8kV/15kV ESD

2.5V (1)

System

VDD

System

Serial

Bus

System

VSS

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:

( SCL > VIH ) OR ( SDA > VIH )

The DS2746 operating mode transitions from ACTIVE to SLEEP when:

SMOD = 1 AND [ ( SCL < VIL ) AND ( SDA < VIL ) ] for tSLEEP

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

measuring VIN, AIN0, and AIN1 in that order. Voltage measurement of each input requires 220ms to complete. A

full sequence of voltage measurements requires 660ms to complete. VOUT is active for a precharge time of tPRE

before the AIN0 measurement time occurs. The VOUT pin is enabled during the entire AIN0 and AIN1 measurement

sequence as long as the VODIS (VOUT Disable) bit is cleared. See Figure 5.

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