MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
Alternatively, the TTE register can be used to estimate time
Cycles Register (17h)
The Cycles register accumulates total percent change in
the cell during both charging and discharging. The result
is stored as a total count of full charge/discharge cycles.
For example, a full charge/discharge cycle results in
the Cycles register incrementing by 100%. The Cycles
register has a full range of 0 to 65535% with a 1% LSb.
This register is reset to 0% at power-up. To maintain the
lifetime cycle count of the cell, this register must be peri-
odically saved by the host and rewritten to the device at
power-up. See the Save and Restore Registers section
for details. See Figure 19 for the Cycles register format.
to empty for any given current load. Whenever the AtRate
register is programmed to a negative number, representing
a discharge current, the TTE register displays the estimated
time to empty for the application based on the AtRate regis-
ter value. Figure 17 shows the TTE register format.
Age Register (07h)
The Age register contains a calculated percentage value
of the application’s present cell capacity compared to its
expected capacity. The result can be used by the host to
gauge the cell’s health as compared to a new cell of the
same type. The result is displayed as a percentage value
from 0 to 256% with a 0.0039% LSb. Figure 18 shows the
Age register format. The equation for the register output is:
VFOCV Register (FBh)
The VFOCV register contains the raw open-circuit volt-
age output of the voltage fuel gauge. This value is used
in other internal calculations and can be read for debug
purposes. The result is a 12-bit value ranging from 2.5V
to 5.119V where 1 LSb is 1.25mV. The bottom 4 bits of
this register are don’t care bits. See Figure 20 for the
VFOCV register format.
Age Register = 100% O (FullCAP Register/
DesignCap Register)
MSB—ADDRESS 11h
LSB—ADDRESS 11h
10
9
8
7
6
5
4
3
2
1
0
-1
-2
-3
-4
-5
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
MSb
LSb
MSb
0
LSb
2 UNITS: 3.0min
Figure 17. TTE Register Format (Output)
MSB—ADDRESS 07h
LSB—ADDRESS 07h
7
6
5
4
3
2
1
0
-1
-2
-3
-4
-5
-6
-7
-8
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
MSb
LSb
MSb
0
LSb
2 UNITS: 1.0%
-8
2
UNITS: 0.0039%
Figure 18. Age Register Format (Output)
MSB—ADDRESS 17h
LSB—ADDRESS 17h
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
MSb
LSb
MSb
0
LSb
2 UNITS: 1.0%
Figure 19. Cycles Register Format (Output)
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