Functional Description

General Operation

The bq2011K determines battery capacity by monitoring

the amount of charge input to or removed from a recharge-

able battery. The bq2011K measures discharge and charge

currents, estimates self-discharge, monitors the battery for

low-battery voltage thresholds, and compensates for tem-

perature and charge/discharge rates. The charge measure-

ment is made by monitoring the voltage across a small-

value series sense resistor between the battery’s negative

terminal and ground. The available battery charge is de-

termined by monitoring this voltage over time and correct-

ing the measurement for the environmental and operating

conditions.

Figure 1 shows a typical battery pack application of the

bq2011K using the LED display with absolute mode as a

charge-state indicator. The absolute display mode uses

the programmed full count (PFC) as the full reference,

forcing each segment of the display to represent a fixed

amount of charge.

A push-button display feature is

available for momentarily enabling the LED display.

The bq2011K monitors the charge and discharge cur-

ure 1). A filter between the negative battery terminal

and the SR pin may be required if the rate of change of

the battery current is too great.

Register Backup

The bq2011K RBI input pin is intended to be used with

a storage capacitor to provide backup potential to the in-

3

bq2011K

FG201103.eps

SPFC

SEG5

SEG4/PROG4

SEG3/PROG3

SEG2/PROG2

SEG1/PROG1

VSS

DISP

SB

VCC

REF

bq2011K

Gas Gauge IC

LCOM

SR

RBI

DQ

VCC

C1

0.1 F

Q1

ZVNL110A

R1

RS

RB1

RB2

Load

Charger

Indicates optional.

Directly connect to VCC across 4 cells (4.8V nominal and should not

exceed 6.5V) with a resistor and a Zener diode to limit voltage during charge.

Otherwise, R1, C1, and Q1 are needed for regulation of >4 cells.

Programming resistors and ESD-protection diodes are not shown.

R-C on SR may be required (application-specific), where the maximum R should not exceed 20K.

Figure 1. Application Diagram: LED Display, Absolute Mode