BQ2040_15 Datasheet, PDF (3/36 Pages) Texas Instruments – Gas Gauge IC With SMBus Interface

Not Recommended For New Designs
bq2040
Functional Description
General Operation
The bq2040 determines battery capacity by monitoring
the amount of charge put into or removed from a re-
chargeable battery. The bq2040 measures discharge
and charge currents, estimates self-discharge, and
monitors the battery for low-battery voltage thresholds.
The charge is measured by monitoring the voltage
across a small-value series sense resistor between the
battery's negative terminal and ground. The available
battery charge is determined by monitoring this voltage
over time and correcting the measurement for the envi-
ronmental and operating conditions.
Figure 1 shows a typical battery pack application of the
bq2040 using the LED capacity display, the serial port,
and an external EEPROM for battery pack program-
ming information. The bq2040 must be configured and
calibrated for the battery-specific information to ensure
proper operation. Table 1 outlines the configuration in-
formation that must be programmed in the EEPROM.
An internal temperature sensor eliminates the need
for an external thermistor—reducing cost and compo-
nents. An internal, temperature-compensated time-
base eliminates the need for an external resonator,
further reducing cost and components. The entire cir-
cuit
in
Figure
1
can
occupy
less
than
3
4
square
inch
of
board space.
VCC
ESCL
ESDA
LED1
LED2
LED3
LED4
VSS
VOUT
REF
SMBC
SMBD
PSTAT
SB
DISP
SR
bq2040
(Optional)
Chart 1
For bq2040 With No D8
No. of Cells
R5
R11 R4
2
301K 604K 100K
3
499K 806K 100K
4
698K 604K 100K
6
499K 499K 100K
8
698K 806K 100K
9
806K 499K 100K
10
909K 604K 100K
12
909K 909K 86.5K
Q1
BSS138
BSS138
2N7002
BSS138
BSS138
2N7002
2N7002
2N7002
(Optional)
Figure 1. Battery Pack Application Diagram—LED Display
2040LED.eps
3