Datasheet

bq27541-G1
www.ti.com SLUSAL6C –NOVEMBER 2011–REVISED OCTOBER 2012
POWER CONTROL
Reset Functions
When the bq27541-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.
Wake-Up Comparator
The wake up comparator is used to indicate a change in cell current while the bq27541-G1 is in SLEEP modes.
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.
Table 21. I
WAKE
Threshold Settings
(1)
IWAKE RSNS1 RSNS0 Vth(SRP-SRN)
0 0 0 Disabled
1 0 0 Disabled
0 0 1 +1.0 mV or –1.0 mV
1 0 1 +2.2 mV or –2.2 mV
0 1 0 +2.2 mV or –2.2 mV
1 1 0 +4.6 mV or –4.6 mV
0 1 1 +4.6 mV or –4.6 mV
1 1 1 +9.8 mV or –9.8 mV
(1) The actual resistance value vs the setting of the sense resistor is not important just the actual voltage
threshold when calculating the configuration. The voltage thresholds are typical values under room
temperature.
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 bq27541-
G1 Vcc voltage does not fall below its minimum of 2.4V during Flash write operations.
AUTOCALIBRATION
The bq27541-G1 provides an autocalibration feature that will measure 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( ) ≤ 100mA
and (2) {voltage change since last offset calibration ≥ 256mV} or {temperature change since last offset calibration
is greater than 8°C for ≥ 60s}.
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 32mV during the offset
calibration, the load current has likely increased considerably; hence, the offset calibration will be aborted.
Copyright © 2011–2012, Texas Instruments Incorporated Submit Documentation Feedback 37
Product Folder Links: bq27541-G1