AD7280AWBSTZ Analog Devices Inc, AD7280AWBSTZ Datasheet - Page 21

• 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

The 10 kΩ resistors in series with the inputs provide protection for
the analog inputs in the event of an overvoltage or undervoltage
on those inputs. The 100 nF capacitor across the differential inputs
acts as a low-pass filter in conjunction with the 10 kΩ resistor.
The cutoff frequency of the low-pass filter is 80 Hz. Using these
external components, the default acquisition time of 400 ns can
be used, which allows a combined acquisition and conversion
time of 1 μs.
CONVERTING CELL VOLTAGES AND AUXILIARY
ADC INPUTS IN A CHAIN OF AD7280As
The AD7280A provides a daisy-chain interface that allows up to
eight parts to be stacked without the need for individual isola-
tion. One feature of the daisy-chain interface is the ability to
initiate conversions on all parts in the daisy-chain stack with a
single convert start command. The convert start command is
transferred up the daisy chain, from the master device to each
AD7280A in turn. The delay time between each AD7280A is
t
start of conversions on the master AD7280A and the last AD7280A
Table 10. Calculated Conversion Times for Three Example AD7280A Configurations, T
Bits
[D15:D14]
00
10
00
DELAY
, as shown in Figure 34. The maximum delay between the
Bits
[D10:D9]
00
00
11
INTERNAL ADC
CONVERSIONS
SERIAL READ
SERIAL READ
OPERATION
OPERATION
PART 1
PART 2
PART 3
CNVST
Bits
[D6:D5]
00
01
10
11
00
01
10
11
00
01
10
11
t
DELAY
Figure 34. ADC Conversions and Readback on a Chain of Three AD7280As
t
DELAY
Configuration
12 channels; t
12 channels; t
12 channels; t
12 channels; t
6 channels; t
6 channels; t
6 channels; t
6 channels; t
12 channels; t
12 channels; t
12 channels; t
12 channels; t
VOLT 6
t
CONV
VOLT 12
VOLT 18
((
t
ACQ
CONV
CONV
CONV
CONV
CONV
CONV
CONV
CONV
CONV
CONV
CONV
CONV
t
VOLT 5
+
DELAY
VOLT 11
t
t
DELAY
= 695 ns; t
= 695 ns; t
= 695 ns; t
= 695 ns; t
CONV
VOLT 17
= 695 ns; t
= 695 ns; t
= 695 ns; t
= 695 ns; t
= 695 ns; t
= 695 ns; t
= 695 ns; t
= 695 ns; t
Rev. 0 | Page 21 of 48
) × (#CONVERSIONS PER PART)) –
t
ACQ
t
ACQ
VOLT 4
t
TOTAL CONVERSION TIME =
VOLT 10
ACQ
ACQ
ACQ
ACQ
ACQ
+ t
ACQ
ACQ
ACQ
ACQ
ACQ
ACQ
ACQ
ACQ
VOLT 16
+ t
CONV
= 465 ns; average = 0
= 1.01 μs; average = 0
= 1.46 μs; average = 0
= 1.89 μs; average = 0
+ t
CONV
= 465 ns; average = 0
= 1.01 μs; average = 0
= 1.46 μs; average = 0
= 1.89 μs; average = 0
= 465 ns; average = 8
= 1.01 μs; average = 8
= 1.46 μs; average = 8
= 1.89 μs; average = 8
CONV
device in the chain can be determined by multiplying t
the number of slave AD7280As in the daisy chain. The total
conversion time for all cell voltage and auxiliary ADC input
conversions can be calculated using the following equation:
where:
t
Table 9).
t
Number of Conversions per Part is the number of inputs selected
for conversion (6, 9, or 12, as listed in Table 8), multiplied by
the number of averages selected for each input (1, 2, 4, or 8).
N is the number of AD7280As in the daisy chain.
t
command between adjacent AD7280A devices, as specified
in Table 3.
The total conversion times calculated for three possible
configurations of the AD7280A are included in Table 10.
ACQ
CONV
DELAY
is the analog input acquisition time of the AD7280A (see
Total Conversion Time = ((t
Conversions per Part)) − t
is the conversion time of the AD7280A, as specified in Table 3.
is the delay time when transferring the convert start
t
ACQ
A
+ ((N – 1) ×
= −40°C to +85°C
Conversion
Time per Part
13.46 μs
19.45 μs
24.4 μs
29.13 μs
6.5 μs
9.22 μs
11.47 μs
13.62 μs
110.9 μs
162.67 μs
205.42 μs
246.27 μs
AUX6
t
DELAY
AUX12
AUX18
ACQ
)
ACQ
+ ((N − 1) × t
+ t
CONV
Total Conversion Time
per 48 Channel Stack
15.2 μs
21.2 μs
26.15 μs
30.9 μs
8.23 μs
10.97 μs
13.22 μs
15.37 μs
112.65 μs
164.42 μs
207.17 μs
248.02 μs
) × (Number of
DELAY
AD7280A
)
DELAY
by