AD7280 Datasheet, PDF (1/33 Pages) Analog Devices – Lithium Ion Battery Monitoring System

Preliminary Technical Data
FEATURES
12-bit ADC, 1us per channel conversion time
6 Analog Input Channels, CM range 0.5V to 27.5V
6 Temperature Measurements Inputs.
On Chip Voltage Regulator
Cell Balancing Interface
Daisy Chain Interface
3 ppm Reference
Low Quiescent Current
High Input Impedance
Serial Interface with Alert Function
1 SPI interface for up to 300 channels
On Chip Registers for Channel Sequencing
VDD Operating Range 7.5V to 30V
Temperature Range -40 ^oC to 105^oC
48 lead LQFP and LFCSP Packages
APPLICATIONS
Lithium Ion Battery Monitoring
Nickel Metal Hydride Battery Monitoring
GENERAL DESCRIPTION
The AD7280¹ contains all the functions required for general
purpose monitoring of stacked Lithium Ion batteries as used in
Hybrid Electric Vehicles. The part has multiplexed analog input
and temperature measurement channels for up to six cells of
battery management. An internal 3-ppm reference is provided
to drive the ADC. The ADC resolution is 12 bits with a 1 Msps
throughput rate offering a 1µs conversion time.
The AD7280 operates from just one VDD supply which has a
range of 7.5V to 30V (with an absolute max rating of 33V). The
part provides 6 pseudo 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 0V to 5V. The input pins assume a series stack of 6
cells. In addition the part can accommodate 6 external sensors
for temperature measurement.
The AD7280 includes on chip registers which allow a sequence
of channel measurements to be programmed to suit the
applications requirements.
Lithium Ion Battery
Monitoring System
AD7280
FUNCTIONAL BLOCK DIAGRAM
VDD
Vin(6)
Vin(5)
Vin(4)
Vin(3)
Vin(2)
Vin(1)
Vin(0)
AD7280
MUX
VT(6)
VT(5)
VT(4)
VT(3)
VT(2)
VT(1)
VT TERM
VREF
CREF
REFGND
DAIS Y CHAIN
INTER FACE
+
+
-
-
CLOCK
2.5V
REF
CB1
CB6
CEL L
BALANCING
INTER FACE
REGUL ATOR
12 BIT ADC
CONTRO L LOGIC
& SELF TEST
LIMIT REG
SQN LOGIC
DATA MEMO RY
SPI INTER FACE
VREG
DGND
DVCC
AVCC
VDRIVE
SCLK
S D IN
SDOUT
ALERT
CS
PD
CNVST
MASTER
Figure 1
The AD7280 also includes an Alert function which generates an
interrupt output signal if the cell voltages exceed an upper or
lower limit defined by the user. The AD7280 has balancing
interface outputs designed to control external FET transistors to
allow discharging of individual cells.
The AD7280 includes a Built In Self Test feature which
internally applies a known voltage to the ADC inputs.
There is a daisy chain interface which allows up to 50 parts to
be stacked without the need for individual device isolation.
The AD7280 requires only one supply pin which takes 7mA
under normal operation, while converting at 1 Msps.
All this functionality is provided in a 48 pin LQFP or 48 pin
LFCSP package operating over a temperature range of −40°C to
+105°C.
1 _{Patents Pending}
Rev. PrD
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