![Texas Instruments bq27441-G1 Скачать руководство пользователя страница 8](http://html1.mh-extra.com/html/texas-instruments/bq27441-g1/bq27441-g1_technical-reference_1095321008.webp)
Chapter 2
SLUUAC9A – December 2013 – Revised May 2015
Functional Description
2.1
Fuel Gauging
The bq27441-G1 battery fuel gauge measures the cell voltage, temperature, and current to determine
battery SOC. The fuel gauge monitors the charging and discharging of the battery by sensing the voltage
across a small-value, external sense resistor (10 m
Ω
, typical) between the SRN and SRP pins. By
integrating the charge passing through the battery, the battery SOC is adjusted during the charging or
discharging of the battery.
The total battery capacity is found by comparing states of charge before and after applying the load with
the amount of charge passed. When an application load is applied, the impedance of the cell is measured
by comparing the OCV obtained from a predefined function for the present SOC with the measured
voltage under load. Measurements of OCV and charge integration determine chemical SOC and chemical
capacity (Qmax). The initial value for Qmax is defined by
Design Capacity
and should match the cell
manufacturers' data sheet. The fuel gauge acquires and updates the battery-impedance profile during
normal battery usage. The impedance profile, SOC, and the Qmax value are used to determine
FullChargeCapacity()
and
StateOfCharge()
, specifically for the present load and temperature.
FullChargeCapacity()
is reported as capacity available from a fully-charged battery under the present load
and temperature until
Voltage()
reaches the
Terminate Voltage
.
NominalAvailableCapacity()
and
FullAvailableCapacity()
are the uncompensated (no or light load) versions of
RemainingCapacity()
and
FullChargeCapacity()
, respectively.
The fuel gauge has two flags,
[SOC1]
and
[SOCF]
, accessed by the
Flags()
command that warn when the
battery SOC has fallen to critical levels. When
StateOfCharge()
falls below the first capacity threshold, as
specified in
SOC1 Set Threshold
, the
[SOC1]
(state-of-charge initial) flag is set. The flag is cleared once
StateOfCharge()
rises above
SOC1 Set Threshold
. All units are in mAh.
When
StateOfCharge()
falls below the second capacity threshold,
SOCF Set Threshold
, the
[SOCF]
(state-of-charge final) flag is set, serving as a final discharge warning. If
SOCF Set Threshold
= –1, the
flag is inoperative during discharge. Similarly, when
StateOfCharge()
rises above
SOCF Clear Threshold
and the
[SOCF]
flag has already been set, the
[SOCF]
flag is cleared. All units are in %.
2.2
Temperature Measurement
The fuel gauge measures temperature via its internal on-chip sensor. This internal temperature data will
be used by the Impedance Track™ algorithm if the
OpConfig [TEMPS]
bit is cleared. Alternatively, if the
OpConfig [TEMPS]
bit is set, the system processor can set the temperature for the fuel gauging algorithm
by writing to the
Temperature()
register.
Regardless of which sensor is used for measurement, the system processor can request the current
battery temperature being used by the algorithm by calling the
Temperature()
function.
2.3
Current Measurement
The fuel gauge measures current by sensing the voltage across a small-value, external sense resistor (10
m
Ω
, typical) between the SRN and SRP pins. Internally, voltage passes through a gain stage before
conversion by the coulomb counter. The current measurement data is available via the
AverageCurrent()
command.
8
Functional Description
SLUUAC9A – December 2013 – Revised May 2015
Copyright © 2013–2015, Texas Instruments Incorporated