BQ26221 Datasheet, PDF (7/20 Pages) Texas Instruments – HIGH PERFORMANCE BATTERY MONITOR IC WITH COUOMB COUNTER, VOLTAGE AND, TEMPERATURE MEASUREMENT

bq26221
PACK+
HDQ
APPLICATION INFORMATION
C3
0.1 µF
C4
0.1 µF
U1
bq26221PW
1 RBI
GPIO 8
Additional ESD
Protection
R5
100 Ω
R4
100 Ω
D1
5.6 V
2 VCC
3 VSS
4 HDQ
SRP 7
SRN 6
BAT 5
Protection Controller
SLUS607 − MAY 2004
+
R2
100 kΩ
C1
0.1 µF
R3
100 kΩ
C2
0.1 µF
R1
0.02 Ω
PACK−
Figure 3. Typical Application Circuit for a Single-Cell Li-Ion Application
UDG−04012
functional description
The bq26221 measures the voltage drop across a low-value series current-sense resistor between the SRP
and SRN pins using a voltage-to-frequency converter. The cell voltage is sensed between the BAT and VSS
pins. All data is placed into various internal counter and timer registers. Using information from the bq26221,
the system host can determine the battery state-of-charge, estimate self discharge, and calculate the average
charge and discharge currents. During pack storage periods, the use of an internal temperature sensor doubles
the self-discharge count rate every 10°C above 25°C. The VFC offset is automatically compensated for in the
charge and discharge counter registers.
Access to the registers and control of the bq26221 is accomplished through a single-wire interface through a
register mapped command protocol. This protocol includes placing the device in the low-power mode,
hardware-register reset, programming flash from RAM, and transferring flash data to RAM.
The bq26221 can operate directly from a single Li-Ion cell as long as V_CC is between 2.8 V and 4.5 V.
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