bq26220

SLUS521B − AUGUST 2002 − REVISED FEBRUARY 2004

7

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APPLICATION INFORMATION

UDG−04012

R2

100 k

Ω

R1

0.02

Ω

C1

0.1

µF

C2

0.1

µF

R3

100 k

Ω

R4

100

Ω

R5

100

Ω

C3

0.1

µF

C4

0.1

µF

1

2

3

4

8

7

6

5

GPIO

SRP

SRN

BAT

RBI

VCC

VSS

HDQ

bq26220PW

U1

+

D1

5.6 V

Additional ESD

Protection

Protection Controller

PACK+

HDQ

PACK−

Figure 3. Typical Application Circuit for a Single-Cell Li-Ion Application

functional description

The bq26220 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 bq26220,

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 bq26220 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.