Modes of operation, Figure 39. max17047 state based on shutd – Rainbow Electronics MAX17047 User Manual
Page 30
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MAX17047
ModelGauge m3 Fuel Gauge
Modes of Operation
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.
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:
• SHUTDOWN command—Write the CONFIG register
SHDN = 1 through the I
2
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.
• I
2
C shutdown—I
2
C lines both persist low for longer
than the SHDNTIMER register value and the CONFIG
register I2CSH = 1.
• 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
section.
These shutdown entry modes are all programmable
according to application. Shutdown events are gated
by the SHDNTIMER register, which allows a long delay
between the shutdown event and the actual shutdown.
By behaving this way, the device takes the best reading
of the relaxation voltage.
Exiting shutdown:
• I2C Wakeup—Any edge on SCL/SDA.
• ALRT Wakeup—Any edge on ALRT line and (ALSH =
1 or I2CSH = ALSH = 0).
• Reset—IC is power cycled.
See the
section for detailed
descriptions of the SHDNTIMER and CONFIG registers.
The state of the device when returning to active mode
differs depending on the triggering event. See
Host software can monitor the POR and Bi status bits to
determine what type of event has occurred.
Figure 39. MAX17047 State Based on Shutdown Exit Condition
BATTERY INSERTION DETECTED
(THRM COMPARATOR RECOGNIZES CHANGE
FROM REMOVAL TO INSERTED STATE)
DNR = 1
Bi = 0
POR = 1
FUEL GAUGE RESET
MaxMinVoltage REGISTER (1Bh) RESET
Cycles REGISTER (17h) RESET
ALL OTHER RAM VALUES MAINTAINED
ALL RAM VALUES MAINTAINED
FUEL GAUGE RESTARTS FROM POINT MAINTAINED
WHEN SHUTDOWN WAS ENTERED
ALL RAM RESET TO DEFAULT VALUES
FUEL GAUGE RESET
POWER-ON RESET
(RECOVERY FROM POWER LOSS)
WAKE FROM SHUTDOWN STATE
(I
2
C EDGE OR ALRT EDGE DETECTED)
EVENT
ACTION
STATUS
INDICATORS
DNR = 1
Bi = 1
POR = UNCHANGED
DNR = 0
Bi = UNCHANGED
POR = UNCHANGED
Figure 39