AD8280WASTZ Analog Devices Inc, AD8280WASTZ Datasheet - Page 15

• Manufacturer Part Number: AD8280WASTZ
• Description: Lithium Ion Battery Safety Monitor
• Manufacturer: Analog Devices Inc

Specifications of AD8280WASTZ

• Function: Battery Monitor
• Battery Type: Lithium-Ion (Li-Ion)
• Voltage - Supply: 6 V ~ 30 V
• Operating Temperature: -40°C ~ 105°C
• Mounting Type: Surface Mount
• Package / Case: 48-LQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

THEORY OF OPERATION
Figure 44 shows a block diagram of the AD8280. The AD8280
is a threshold monitor that can be used to monitor up to six cell
voltages and two temperature voltages. The part can also be used
in a daisy-chain configuration to monitor as many cells as required.
The benefit of the daisy-chain configuration is that isolation is
required to bring the alarm signal away from the high voltage
environment on only the bottom part of the chain, reducing
system cost and minimizing the board space required.
The cell and temperature voltage inputs are connected to the part
using the VIN0 through VIN6 inputs and the VT1 and VT2 inputs,
respectively. Because the six-cell stack voltage can be up to 30 V,
the input voltages are level-shifted and referenced to the lowest
potential (part ground or VBOTx) of the AD8280. These voltages
are then input into window comparators and compared to trip
points set by external resistor dividers.
If the cell or temperature voltage inputs exceed or fall below the
selected trip points, an alarm, in the form of a digital voltage level,
changes state at the voltage output (AVOUTxx) of the part. The
alarm state also exists in the form of a current output (AIOUTxx)
used to communicate to the other devices when multiple parts
are used in a daisy-chain configuration.
The part contains programmable deglitching circuitry to ensure
that transient voltages appearing at the cell inputs are ignored.
VBOT2S
VBOT1S
VTOPS
VBOT2
VBOT1
VIN6
VIN5
VIN4
VIN3
VIN2
VIN0
VIN1
VT1
VT2
VTOP
AD8280
OT
LDO
LDO
SHIFTER
SHIFTER
OT
LEVEL
LEVEL
LDOS
REF
OT
REF
FB
C6O
C6U
C1O
C1U
CT1
CT2
Figure 44. Functional Block Diagram
AIOUTOV
GLITCHING
GLITCHING
GLITCHING
GLITCHING
GLITCHING
GLITCHING
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DE-
DE-
DE-
DE-
DE-
DE-
UV
OV
AIOUTUV
AIINOV
CONVERTER
CONVERTER
The part also contains its own LDO and reference. The LDO
can be used to drive external components such as thermistors
or isolators, whereas the reference can be used with the voltage
dividers to establish the trip points.
The AD8280 has the following unique features and capabilities:
•
•
•
•
•
ALARM
LOGIC
I/V
V/I
AIINUV AIINOT
AIOUTOT
Three, four, five, or six cells can be monitored.
Negative or positive temperature coefficient thermistors
can be used.
Multiple parts can be configured in a daisy chain to monitor
hundreds of cells. Information about the status of the alarms
on the entire daisy chain, as well as input signals that enable
the part and initiate self-test, are all communicated via the
bottom, or master, part in the chain.
Alarm outputs for overvoltage, undervoltage, and overtemp-
erature status can be shared, with each output indicating
the same status for any of the occurring alarm conditions,
or the alarm outputs can function as separate entities with
each indicating the status of the specific condition.
An extensive self-test feature ensures that the internal
components are functioning correctly. The self-test is
initiated upon request to the TESTI pin.
SHIFTER
LEVEL
ENBO
ENBI
GENERATOR
TESTI
SELF-
TEST
TESTO
SEL0
DGT0
SEL 1
DGT1
DGT2
GND2
GND1
TOP
AVOUTOV
AVOUTUV
AVOUTOT
ALRMSEL
VCC
VCCS
NPTC
BOT
AD8280