AD7280ABSTZ datasheet(17/48 Pages) AD

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AD7280A

Rev. 0 | Page 17 of 48

TYPICAL CONNECTION DIAGRAMS

VIN6

VREG

0.1µF

10µF

1µF

0.1µF

CB6

VIN5

CB5

VIN4

CB4

VIN3

CB3

VIN2

CB2

VIN1

CB1

VIN0

VDD

VSS

DVCC

AVCC

1µF

0.1µF

VREF

CREF

ALERT

CNVST

SDO

SCLK

SDI

VDRIVE

MASTER

AD7280A

10kΩ

OPTIONAL INTERFACE PINS

4-WIRE SPI INTERFACE

DSP/MICRO-

PROCESSOR

Figure 28. AD7280A Configuration Diagram for Six Battery Cells

The AD7280A can be used to monitor four, five, or six battery

cells connected in series. A typical configuration for a six-cell

battery monitoring application is shown in Figure 28. However,

lithium ion battery applications require a significant number of

individual cells to provide the required output voltage. Figure 29

shows the recommended configuration of a chain of AD7280As

monitoring a larger battery stack. The daisy-chain interface of the

AD7280A allows each individual AD7280A to communicate with

the AD7280A immediately above and below it. The daisy-chain

interface allows the AD7280As to be electrically connected to

the battery management chip without the need for individual

isolation devices between each AD7280A.

As shown in Figure 29, it is recommended that a Zener diode be

placed across the supplies of each AD7280A. This prevents an

overvoltage across the supplies of each AD7280A during the

initial connection of the daisy chain of AD7280As to the battery

stack. A voltage rating of 30 V is suggested for this Zener diode,

but lower values can also be used to suit the application.

The 10 kΩ resistor in series with the inputs combined with a

100 nF capacitor across the adjacent differential inputs acts as

a low-pass filter. The 10 kΩ resistors provide protection for the

analog inputs in the event of an overvoltage or undervoltage on

those inputs, for example, if any of the cell voltage inputs is

incorrectly shorted to VDD or VSS. The resistors also provide

protection during the initial connection of the daisy chain of

AD7280As to the battery stack. For more information about the

daisy-chain interface, see the Daisy-Chain Interface section.

In an application that includes a safety mechanism designed to

open circuit the battery stack, additional isolation is required

between the AD7280A above the break point and the battery

management chip.

A suggested configuration for the external cell balancing circuit

is shown in Figure 28. This configuration also includes 10 kΩ

resistors in series with the cell balance outputs. These resistors

provide protection for the cell balance outputs in the event of

an overvoltage or undervoltage on those inputs. See the Cell

Balancing Outputs section for more information.

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