AD7280A Datasheet, PDF (1/48 Pages) Analog Devices – Lithium Ion Battery Monitoring System Cell balancing interface

Lithium Ion Battery Monitoring System
AD7280A
FEATURES
12-bit ADC, 1 μs per channel conversion time
6 analog input channels, common-mode
range 0.5 V to 27.5 V
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
High input impedance
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
VDD operating range: 8 V to 30 V
Temperature range: −40°C to +105°C
48-lead LQFP
Qualified for automotive applications
APPLICATIONS
Lithium ion battery monitoring
Electric and hybrid electric vehicles
Power supply backup
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 ±1.6 mV. The ADC resolution is 12 bits and
allows conversion of up to 48 cells within 7 μs.
The AD7280A operates from a single VDD supply that has a
range of 8 V to 30 V (with an absolute maximum rating of
33 V). The part provides six differential analog input channels
to accommodate large common-mode signals across the full
VDD range. Each channel allows an input signal range, VIN(+)
− VIN(−), of 1 V to 5 V. 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.
1 _{Patents pending.}
Rev. 0
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FUNCTIONAL BLOCK DIAGRAM
VIN6
VIN5
VIN4
VIN3
VIN2
VIN1
VIN0
AUX6
AUX5
AUX4
AUX3
AUX2
AUX1
AUX_TERM
V_REF
C_REF
REFGND
V_DD
HV
MUX
DAISY-CHAIN
INTERFACE
AD7280A
CELL
BALANCING
INTERFACE
REGULATOR
LV
MUX
12-BIT ADC
CLOCK
CONTROL LOGIC
AND SELF-TEST
2.5V
REF
LIMIT REG
SQN LOGIC
DATA MEMORY
SPI INTERFACE
V_SS AGND
SDOlo ALERTlo
Figure 1.
V_REG
DGND
DV_CC
AV_CC
V_DRIVE
SCLK
SDI
SDO
ALERT
CS
PD
CNVST
MASTER
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 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.
The AD7280A requires only one supply pin that accepts 6.9 mA
under normal operation while converting at 1 MSPS.
All this functionality is provided in a 48-lead LQFP package
operating over a temperature range of −40°C to +105°C.
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