MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
Both these registers are signed two’s complement. The
when temperature measurements are complete. This fea-
ture limits the time the external resistor-divider network
is active and lowers the total amount of energy used by
the system.
default values of 4000h for CGAIN and 0000h for COFF
preserve factory calibration and unit values (1.5625FV).
Figure 55 shows the CGAIN register format and Figure 56
shows the COFF register format.
When Tex = 0 and Ten = 1 in the CONFIG register, the
device converts the AIN register to a temperature using
the temperature gain (TGAIN) and temperature offset
(TOFF) register values:
Temperature Measurement
While in active mode and Ten = 1 in the CONFIG register,
the device periodically measures the voltage between
the AIN and CSP pins and compares the result to the volt-
age of the THRM pin. The device stores the result, a ratio-
metric value from 0 to 100%. The resulting data is placed
in the AIN register every 1.4s with an LSb of 0.0122%.
Temperature Register = (AIN Register O
TGAIN Register/16384) + (TOFF Register O 2)
The resulting value is stored in the Temperature register
each time the AIN register is updated. Additionally, the
device maintains a record of the minimum and maximum
temperature measured by the device, and an average
temperature over a time period defined by the host.
Table 4 lists the recommended TGAIN and TOFF register
values for common NTC thermistors.
Conversions are initiated by connecting the THRM and
VTT pins internally. This enables the active pullup to
the external voltage-divider network. After the pullup is
enabled, the device waits for a settling period of t
PRE
prior to making measurements on the AIN pin. When
ETHRM = 1, FTHRM = 0, the active pullup is disabled
MSB—ADDRESS 2Eh
LSB—ADDRESS 2Eh
0
-1
-2
-3
-4
-5
-6
-7
-8
-9
-10
-11
-12
-13
-14
S
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
MSb
LSb
MSb
0
LSb
2 UNITS: 0.0061%
Figure 55. CGAIN Register Format (Input)
MSB—ADDRESS 2FH
LSB—ADDRESS 2Fh
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
S
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
MSb
LSb
MSb
UNITS: 3.125FV/R
LSb
SENSE
Figure 56. COFF Register Format (Input)
Table 4. Recommended TGAIN and TOFF Register Values for Common NTC
Thermistors
THERMISTOR
R
(kI)
BETA
RECOMMENDED TGAIN
RECOMMENDED TOFF
25C
Semitec
103AT-2
10
3435
E3E1h
290Eh
Fenwal
197-103LAG-A01
10
10
3974
4550
E71Ch
E989h
251Ah
22B1h
TDK
Type F
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