BQ2052_15 Datasheet, PDF (3/20 Pages) Texas Instruments – Gas Gauge IC

Not Recommended For New Designs
Preliminary bq2052
Functional Description
Measurements
General Operation
The bq2052 determines battery capacity by monitoring
the amount of charge removed from a primary battery.
The bq2052 measures discharge currents and battery
voltage, monitors the battery for the low battery-voltage
thresholds, and compensates available capacity for tem-
perature and discharge rate. The bq2052 measures ca-
pacity by monitoring the voltage across a small-value se-
ries sense resistor between the negative battery termi-
nal and ground.
Figure 1 shows a typical battery pack application of the
bq2052 using the LED display capability as a
charge-state indicator. The bq2052 displays capacity
with two, four, or five LEDs using the programmed full
count (PFC) as the battery’s “full” reference. The bq2052
has a push-button input for momentarily enabling the
LED display.
The bq2052 uses a voltage-to-frequency converter (VFC)
for discharge measurement and an analog-to-digital con-
verter (ADC) for battery voltage measurement.
Discharge Counting
The VFC measures the discharge flow of the battery by
monitoring a small value sense resistor between the SR
pin and V_SS as shown in Figure 1. The bq2052 detects
“discharge” activity when the potential at the SR input,
V_SRO, is positive. The bq2052 integrates the signal over
time using an internal counter. The fundamental rate of
the counter is 3.125µVh. The VFC measures signals up
to 0.5V in magnitude.
Digital Magnitude Filter
The bq2052 has a digital filter to eliminate discharge
counting below a set threshold. The minimum discharge
threshold, V_SRD, for the bq2052 is 250µV.
H or L
To µC
bq2052
Gas Gauge IC
REF
LCOM
SEG1
SEG2
SEG3
SEG4
SEG5
PROG6
CP
HDQ
VCC
SB
DISP
VSS
SR
RBI
R1
Q1
ZVNL110A
C1
RB1
RB2
100K
RS
0.1µF
Notes:
1.
Indicates optional.
2. V_CC can connect directly to two lithium primary cells
(6.0V nominal and should not exceed 6.5V).
Otherwise, R1, C1, and Q1 are needed for regulation of > 2 cells.
3. Programming resistors and ESD-protection diodes are not shown.
4. R-C on SR is required.
5. A series diode is required on RBI if the bottom series cell is used as the backup source.
If the cell is used, the backup capacitor is not required, and the anode is connected to the
positive terminal of the cell.
Load
FG205201.eps
Figure 1. Application Diagram—5-Segment LED Display
3