Current measurement, Current register (0ah), Figure 50. maxminv register format (outp – Rainbow Electronics MAX17047 User Manual
Page 36: Figure 51. current register format (outp, Table 3. sample current register convers, Table 3. sample current register conversions
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MAX17047
ModelGauge m3 Fuel Gauge
values. If V
CELL
is larger than the maximum or less than
the minimum, the corresponding value is replaced with
the new reading. At power-up, the MaxV
CELL
value is set
to 00h (the minimum) and the MinV
CELL
value is set to
FFh (the maximum). Therefore, both values are changed
to the V
CELL
register reading after the first update. Host
software can reset this register by writing it to its power-
up value of 00FFh. The maximum and minimum voltages
are each stored as 8-bit values with a 20mV resolution.
shows the MaxMinV
CELL
register format.
Current Measurement
While in active mode, the device periodically measures
the voltage between the CSN and CSP pins over a
Q
51.2mV range. The resulting data is stored as a signed
two’s-complement value in the Current register every
175.8ms with an LSb value of 1.5625FV/R
SENSE
. All
devices are calibrated for current-measurement accu-
racy at the factory. However, if the application requires,
Current Register readings can be adjusted by changing
the COFF and CGAIN register settings.
Additionally, the device maintains a record of the mini-
mum and maximum current measured by the device,
and an average current over a time period defined by
the host. Contents of the Current and AverageCurrent
registers are 0000h until the first conversion cycle time
period after IC power-up. The last values of the Current
and AverageCurrent registers are maintained when the
IC enters shutdown mode.
Current Register (0Ah)
While in active mode, the device periodically measures the
voltage between the CSN and CSP pins over a Q51.2mV
range. The resulting data is stored as a two’s-complement
value in the Current register every 175.8ms with an LSb value
of 1.5625FV/R
SENSE
. Voltages outside the minimum and
maximum register values are reported as the minimum or
maximum value.
shows the Current register format
shows the Sample Current register conversions.
Figure 51. Current Register Format (Output)
Figure 50. MaxMinV
CELL
Register Format (Output)
Table 3. Sample Current Register Conversions
FUNCTION
SENSE
RESISTOR (I)
CGAIN
REGISTER
CURRENT REGISTER
RESOLUTION (µA)
CURRENT REGISTER
RANGE (A)
MAXIMUM CELL
CAPACITY (Ah)
Adjusting sense
resistor to meet
range and accuracy
requirements
0.005
4000h
312.50
Q
10.24
32.768
0.010
4000h
156.25
Q
5.12
16.384
0.020
4000h
78.125
Q
2.56
8.192
Adjusting CGAIN to
keep units constant
0.005
8000h
156.25
Q
5.12
16.384
0.010
4000h
156.25
Q
5.12
16.384
0.020
2000h
156.25
Q
5.12
16.384
Figure 51
MSB—ADDRESS 0Ah
LSB—ADDRESS 0Ah
S
2
14
2
13
2
12
2
11
2
10
2
9
2
8
2
7
2
6
2
5
2
4
2
3
2
2
2
1
2
0
MSb
LSb
MSb
LSb
UNITS: 1.5625FV/R
SENSE
Figure 50
MSB—ADDRESS 1Bh
LSB—ADDRESS 1Bh
MAX
7
MAX
6
MAX
5
MAX
4
MAX
3
MAX
2
MAX
1
MAX
0
MIN
7
MIN
6
MIN
5
MIN
4
MIN
3
MIN
2
MIN
1
MIN
0
MSb
LSb
MSb
LSb
UNITS: 20mV