BQ2052_15 Datasheet, PDF (4/20 Pages) Texas Instruments – Gas Gauge IC

Not Recommended For New Designs
bq2052 Preliminary
Table 1. bq2052 Current-Sensing Errors
Symbol
INL
INR
Parameter
Integrated non-linearity
error
Integrated non-
repeatability error
Typical
±2
±1
Maximum
±4
±2
Units
%
%
Notes
Add 0.1% per °C above or below 25°C
and 1% per volt above or below 4.25V.
Measurement repeatability given
similar operating conditions.
Voltage Monitoring and Thresholds
In conjunction with monitoring the SR input for dis-
charge currents, the bq2052 monitors the battery poten-
tial through the SB pin. The voltage at the SB pin, V_SB,
is developed through a high impedance resistor network
connect across the battery. The bq2052 monitors the
voltage at the SB pin and reports the voltage in the VSB
register (address = 0bh).
The bq2052 compares the V_SB reading to two
end-of-discharge voltage (EDV) thresholds. The EDV
threshold levels are used to determine when the battery
has reached an “empty” state. The EDV thresholds for
the bq2052 are programmable with the default values
fixed at:
EDV1 (first) = 0.76V
EDVF (final) = EDV1 - 0.10V = 0.66V
If V_SB is below either of the two EDV thresholds for 8
consecutive samples over a 4 second period, the bq2052
sets the associated flag in the FLGS1 register (address =
01h). Once set, the EDV flags remain set, independent
of V_SB.
Temperature
The bq2052 has an internal temperature sensor to mea-
sure temperature. The bq2052 determines the tempera-
ture and stores it in the TEMP register (address = 02h).
The bq2052 uses temperature to adapt remaining capac-
ity for the battery’s discharge efficiency.
Gas Gauge Operation
General
The operational overview diagram in Figure 2 illus-
trates the operation of the bq2052. The bq2052 accumu-
lates a measure of discharge currents and calculates
available capacity. The bq2052 compensates available
capacity for discharge rate and temperature and pro-
vides the information in the Compensated Available Ca-
pacity (CAC) registers (address = 0eh–0fh). The main
counter, Discharge Count Register (DCR) (address =
2eh), represents the cumulative amount of charge re-
moved from the battery. Battery discharging increments
the DCR register.
Inputs
Discharge
Current
Rate and
Temperature
Efficiency
Factor
Main Counters
+
Discharge
Count
Register
(DCR)
Full Nominal
Available Charge
(FNAC)
+
–
Compensated
Available
Capacity
(CAC)
Complete
Data Set
Outputs
Chip-Controlled
Available Charge
LED Display
Serial Port
FG2052.eps
Figure 2. Operational Overview
4