BQ27546-G1 Datasheet, PDF (11/38 Pages) Texas Instruments – nullSingle-Cell Li-Ion Battery Fuel Gauge

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bq27546-G1
SLUSC53A – MAY 2015 – REVISED DECEMBER 2015
Feature Description (continued)
9.3.3 Power Control
9.3.3.1 Reset Functions
When the bq27546-G1 detects a software reset by sending [RESET] Control() subcommand, it determines the
type of reset and increments the corresponding counter. This information is accessible by issuing the command
Control() function with the RESET_DATA subcommand.
9.3.3.2 Wake-Up Comparator
The wake-up comparator is used to indicate a change in cell current while the bq27546-G1 is in SLEEP mode.
Pack Configuration uses bits [RSNS1–RSNS0] to set the sense resistor selection. Pack Configuration also
uses the [IWAKE] bit to select one of two possible voltage threshold ranges for the given sense resistor
selection. An internal interrupt is generated when the threshold is breached in either charge or discharge
directions. Setting both [RSNS1] and [RSNS0] to 0 disables this feature.
IWAKE
0
1
0
1
0
1
0
1
Table 1. I_WAKE Threshold Settings⁽¹⁾
RSNS1
RSNS0
Vth(SRP-SRN)
0
0
Disabled
0
0
Disabled
0
1
+1.0 mV or –1.0 mV
0
1
+2.2 mV or –2.2 mV
1
0
+2.2 mV or –2.2 mV
1
0
+4.6 mV or –4.6 mV
1
1
+4.6 mV or –4.6 mV
1
1
+9.8 mV or –9.8 mV
(1) The actual resistance value vs. the sense resistor setting is not important; however, the actual voltage
threshold when calculating the configuration is important. The voltage thresholds are typical values
under room temperature.
9.3.3.3 Flash Updates
Data flash can only be updated if Voltage() ≥ Flash Update OK Voltage. Flash programming current can cause
an increase in LDO dropout. The value of Flash Update OK Voltage should be selected such that the bq27546-
G1 V_CC voltage does not fall below its minimum of 2.4 V during flash write operations.
9.3.4 Autocalibration
The bq27546-G1 device provides an autocalibration feature that measures the voltage offset error across SRP
and SRN from time-to-time as operating conditions change. It subtracts the resulting offset error from normal
sense resistor voltage, V_SR, for maximum measurement accuracy.
Autocalibration of the ADC begins on entry to SLEEP mode, except if Temperature() is ≤ 5°C or Temperature() ≥
45°C.
The fuel gauge also performs a single offset calibration when (1) the condition of AverageCurrent() ≤ 100 mA
and (2) {voltage change since the last offset calibration ≥ 256 mV} or {temperature change since last offset
calibration is greater than 8°C for ≥ 60 seconds}.
Capacity and current measurements will continue at the last measured rate during the offset calibration when
these measurements cannot be performed. If the battery voltage drops more than 32 mV during the offset
calibration, the load current has likely increased considerably; therefore, the offset calibration will be stopped.
Copyright © 2015, Texas Instruments Incorporated
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