Lithium Ion Battery Monitoring System
AD7280A
FUNCTIONAL BLOCK DIAGRAM
FEATURES
12-bit ADC, 1 μs per channel conversion time
6 analog input channels, common-mode
range 0.5 V to 27.5 V
V
DD
6 auxiliary ADC inputs
1.6 mV cell voltage accuracy
On-chip voltage regulator
Cell balancing interface
Daisy-chain interface
Internal reference: 3 ppm/oC
1.8 μA power-down current
DAISY-CHAIN
INTERFACE
CELL
BALANCING
INTERFACE
VIN6
VIN5
VIN4
VIN3
VIN2
VIN1
VIN0
HV
MUX
V
REGULATOR
12-BIT ADC
AD7280A
REG
DGND
DV
AV
CC
CC
AUX6
AUX5
AUX4
AUX3
AUX2
AUX1
High input impedance
V
DRIVE
LV
MUX
Serial interface with alert function
1 SPI interface for up to 48 channels
CRC protection on read and write commands
On-chip registers for channel sequencing
CONTROL LOGIC
AND SELF-TEST
CLOCK
SCLK
SDI
SDO
ALERT
CS
PD
AUX
TERM
LIMIT REG
SQN LOGIC
DATA MEMORY
SPI INTERFACE
V
C
REF
REF
2.5V
REF
VDD operating range: 8 V to 30 V
Temperature range: −40°C to +105°C
48-lead LQFP
REFGND
CNVST
MASTER
Qualified for automotive applications
APPLICATIONS
V
AGND
SDOlo ALERTlo
SS
Lithium ion battery monitoring
Electric and hybrid electric vehicles
Power supply backup
Figure 1.
Power tools
GENERAL DESCRIPTION
The AD7280A1 contains all the functions required for general-
purpose monitoring of stacked lithium ion batteries as used in
hybrid electric vehicles, battery backup applications, and power
tools. The part has multiplexed cell voltage and auxiliary ADC
measurement channels for up to six cells of battery management.
An internal 3 ppm/°C reference is provided that allows a cell
voltage accuracy of 1.ꢀ mꢁ. The ADC resolution is 12 bits and
allows conversion of up to 48 cells within 7 μs.
The AD7280A includes on-chip registers that allow a sequence
of channel measurements to be programmed to suit the application
requirements.
The AD7280A also includes a dynamic alert function that can
detect whether the cell voltages or auxiliary ADC inputs exceed
an upper or lower limit defined by the user. The AD7280A has
cell balancing interface outputs designed to control external FET
transistors to allow discharging of individual cells.
The AD7280A operates from a single ꢁDD supply that has a
range of 8 ꢁ to 30 ꢁ (with an absolute maximum rating of
33 ꢁ). The part provides six differential analog input channels
to accommodate large common-mode signals across the full
The AD7280A includes a built-in self-test feature that internally
applies a known voltage to the ADC inputs.
A daisy-chain interface allows up to eight parts to be stacked
without the need for individual device isolation.
ꢁDD range. Each channel allows an input signal range, ꢁIN(+)
The AD7280A requires only one supply pin that accepts ꢀ.9 mA
under normal operation while converting at 1 MSPS.
− ꢁIN(−), of 1 ꢁ to 5 ꢁ. The input pins assume a series stack of
six cells. In addition, the part includes six auxiliary ADC input
channels that can be used for temperature measurement or
system diagnostics.
All this functionality is provided in a 48-lead LQFP package
operating over a temperature range of −40°C to +105°C.
1 Patents pending.
Rev. 0
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