AD7280AWBSTZ Analog Devices Inc, AD7280AWBSTZ Datasheet - Page 27

• Manufacturer Part Number: AD7280AWBSTZ
• Description: IC BATT MON LI-ION AUTO 48LQFP
• Manufacturer: Analog Devices Inc
• Series: -r

Specifications of AD7280AWBSTZ

• Function: Battery Monitor, Over/Under Voltage Protection
• Battery Chemistry: Lithium-Ion (Li-Ion)
• Voltage - Supply: 8 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

ALERT OUTPUT
The alert output on the AD7280A can be used to indicate
whether any of the following faults has occurred:
•
•
•
•
Following each completed conversion, the cell voltage and
auxiliary ADC measurement results are compared to the alert
thresholds. The alert thresholds are set by writing to the cell
overvoltage, cell undervoltage, AUX ADC overvoltage, and
AUX ADC undervoltage registers. An alert output is generated
if the cell voltage and/or the auxiliary ADC results are outside
the programmed alert thresholds.
The alert output can be configured as a static or dynamic output
by writing to the alert register. The static alert output is a high
signal that is pulled low in the event of an overvoltage or under-
voltage on the cell voltage or auxiliary ADC input conversions.
The dynamic alert is a square wave that can be programmed to
a frequency of 100 Hz, 1 kHz, or 10 kHz. The alert output can
be used as part of a daisy chain, in which case the AD7280A at
the top of the chain, that is, farthest away from the DSP/micro-
processor, should be programmed to generate the initial alert
output, and all other devices in the chain should be programmed
to allow the alert signal to pass through. If a conversion result
outside the programmed thresholds occurs, either on the device
generating the initial alert signal or on any device in the chain,
the alert signal is pulled low to indicate that an alert condition
has occurred. At the end of the daisy chain, the master AD7280A,
which is connected to the DSP/microprocessor, takes the alert
signal from the chain and passes it in standard digital voltage
format to the DSP/microprocessor. The configuration settings
for the alert register are described in Table 11 and Table 12.
Table 11. Alert Register Settings, Bits[D7:D4]
Bits[D7:D6]
00
01
10
10
10
10
11
1
X is don’t care.
Cell overvoltage
Cell undervoltage
Auxiliary ADC overvoltage
Auxiliary ADC undervoltage
Bits[D5:D4]
XX
XX
00
01
10
11
XX
Action
No alert signal generated or
passed (default)
Generates a static (high) alert
signal to be passed down the
daisy chain
Generates a 100 Hz square wave
alert signal to be passed down
the daisy chain
Generates a 1 kHz square wave
alert signal to be passed down
the daisy chain
Generates a 10 kHz square wave
alert signal to be passed down
the daisy chain
Reserved
Passes an alert signal from the
AD7280A at higher potential in
the daisy chain
1
Rev. 0 | Page 27 of 48
Table 12. Alert Register Settings, Bits[D3:D0]
Bits[D3:D2]
00
01
10
11
XX
XX
XX
XX
1
2
3
Some applications require fewer than six voltage measurements
(see the Connection of Fewer Than Six Voltage Cells section).
As shown in Figure 35, it is recommended that a channel that
is not being used on the AD7280A be shorted to the channel
below it. To prevent the incorrect triggering of the alert output
in this application, the AD7280A allows the user to select up to
two voltage channels that can be taken out of the overvoltage/
undervoltage detection circuit. This is programmed through
Bits[D3:D2] of the alert register. The user can also remove all
or selected auxiliary ADC channels from the detection circuit.
This is programmed through Bits[D1:D0] of the alert register in
combination with Bits[D15:D14] of the control register.
The operation of the alert output can be verified by initiating a
self-test conversion. The self-test conversion converts the band
gap reference voltage, 1.2 V, which triggers an alert output if the
cell undervoltage threshold is set higher than 1.2 V. To test the
alert output, a self-test conversion should be initiated on the
AD7280A farthest away from the DSP/microprocessor.
The operation of the alert output can also be verified by increas-
ing or decreasing the thresholds around a known input voltage
to trigger an alert condition. The alert operation of each device
in the daisy chain of AD7280As can be verified by, for example,
decreasing the cell overvoltage threshold of that device below the
value of the input voltage on the cells. Initiating a conversion on
all devices in the daisy chain pulls the alert signal low as it passes
through that device. The relevant threshold on that device can
then be returned to its previous value and the process repeated
on the next device in the daisy chain.
X is don’t care.
Includes six auxiliary ADC channels in the alert detection if conversions on
six auxiliary ADC channels are selected in the control register; includes three
auxiliary ADC channels in the alert detection if conversions on three auxiliary
ADC channels are selected in the control register.
To remove AUX5 or AUX5 and AUX3 from the alert detection, conversions on
three auxiliary ADC input channels only must be selected in the control register.
Bits[D1:D0]
XX
XX
XX
XX
00
01
10
11
Action
Includes all six voltage channels in
alert detection (default)
Removes VIN5 from alert
detection
Removes VIN5 and VIN4 from alert
detection
Reserved
Includes all AUX ADC channels
selected for conversion in alert
detection
Removes AUX5 from alert
detection
Removes AUX5 and AUX3 from
alert detection
Reserved
2
3
(default)
3
1
AD7280A