MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
Cell Removal
Modes of Operation
The device detects a cell removal if either the ETHRM or
FTHRM bits of the CONFIG register are set to enable the
THRM pin output. Cell removal does not affect IC opera-
tion. The device continues to update fuel-gauge outputs.
The host should monitor the Br and Bst bits of the Status
register to determine if the fuel-gauge outputs are valid.
The device operates in one of two power modes: active
and shutdown. While in active mode, the device oper-
ates as a high-precision battery monitor with tempera-
ture, voltage, auxiliary inputs, current, and accumulated
current measurements acquired continuously, and the
resulting values updated in the measurement registers.
READ and WRITE access is allowed only in active mode.
The device can also be configured to alert the host when
cell removal occurs. When Ber = 1 in the CONFIG regis-
ter, the device generates an interrupt on the ALRT pin at
the start of the first temperature conversion after removal.
This could take up to 1.4s to occur. This feature is useful
if the application uses more than one cell type and the IC
must be reconfigured at each insertion.
In shutdown mode, the LDO is disabled and all activ-
ity stops, although volatile RAM contents remain pre-
served. All A/D register and fuel-gauge output values
are maintained. There are several options for entering
shutdown:
Entering shutdown:
Fast Detection of Cell Removal
The device can be configured to quickly alert the host of
impending power loss on cell removal. This fast response
allows the system to quickly and gracefully hibernate to
prevent power loss during battery swap. When Ber = 1 and
FTHRM = 1 in the CONFIG register, an interrupt on the
•ꢀ SHUTDOWN command—Write the CONFIG register
2
SHDN = 1 through the I C interface; wait for longer
than the SHDNTIMER register value.
•ꢀ Pack removal—Pack removal detection is valid for
longer than the SHDNTIMER register value and the
CONFIG register AINSH = 1.
ALRT pin is generated within 100Fs after V
becomes
AIN
greater than V
- V
. If fast detection is used, it
DETR
THRM
2
2
•ꢀ I C shutdown—I C lines both persist low for longer
than the SHDNTIMER register value and the CONFIG
register I2CSH = 1.
is recommended that all other IC interrupts are disabled
to prevent the host from spending time determining the
cause of the interrupt. Fast detection of cell removal has
no affect on fuel-gauge operation, but leaving the exter-
nal resistor-divider active increases current consumption
of the application. See Figure 39.
•ꢀ ALRT shutdown—Shutdown occurs when the ALRT
line is externally driven low for longer than the
SHDNTIMER register value (ALSH = 1 and ALRTp =
0), or the ALRT line is externally driven high for longer
than the SHDNTIMER register value (ALSH = 1 and
ALRTp = 1). See the CONFIG Register (1Dh) section.
CELL REMOVAL
(Ber = 1, FTHRM = 1)
V
BATT
AIN
< 100µs
ALRT
OUTPUT
CELL REMOVAL
INTERRUPT GENERATED
Figure 39. Fast Detection of Cell Removal
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