Datasheet
AD7280A
Rev. 0 | Page 17 of 48
TYPICAL CONNECTION DIAGRAMS
VIN6
V
REG
0.1µF 10µF
1µF
0.1µF
0.1µF
CB6
VIN5
CB5
VIN4
CB4
VIN3
CB3
VIN2
CB2
VIN1
CB1
VIN0
V
DD
V
SS
DV
CC
AV
CC
1µF
0.1µF
V
REF
C
REF
ALERT
CNVST
PD
SDO
SCLK
SDI
CS
V
DRIVE
MASTER
AD7280A
10kΩ
10kΩ
10kΩ
10kΩ
10kΩ
10kΩ
10kΩ
10kΩ
10kΩ
10kΩ
10kΩ
10kΩ
10kΩ
10kΩ
OPTIONAL INTERFACE PINS
4-WIRE SPI INTERFACE
DSP/MICRO-
PROCESSOR
09435-010
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 k 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 k 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 V
DD
or V
SS
. 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 k
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.