Features

Multifunction charge/discharge

counter

Resolves signals less than 12.5μV

Internal offset calibration improves

accuracy

1024 bits of NVRAM configured as

128 x 8

Internal temperature sensor for

self-discharge estimation

Single-wire serial interface

Dual operating modes:

- Operating: <80μA

- Sleep: <10μA

REG output for low-cost microregulation

Internal timebase eliminates external

components

8-pin TSSOP or SOIC allows battery

pack integration

General Description

The bq2018 is a low-cost charge/discharge

counter peripheral packaged in

an 8-pin TSSOP or SOIC. It works

with an intelligent host controller, providing

state-of-charge information for

rechargeable batteries.

The bq2018 measures the voltage

drop across a low-value series sense

resistor between the negative terminal

of the battery and the battery

pack ground contact. By using the accumulated

counts in the charge,

discharge, and self-discharge registers,

an intelligent host controller can

determine battery state-of-charge information.

To improve accuracy, an

offset count register is available. The

system host controller is responsible

for the register maintenance by resetting

the charge in/out and selfdischarge

registers as needed.

The bq2018 also features 128 bytes

of NVRAM registers. The upper 13

bytes of NVRAM contain the capacity

monitoring and status information.

The RBI input operates from

an external power storage source

such as a capacitor or a series cell in

the battery pack, providing register

nonvolatility for periods when the

battery is shorted to ground or when

the battery charge state is not sufficient

to operate the bq2018. During

this mode, the register backup current

is less than 100nA.

Packaged in an 8-pin TSSOP or

SOIC, the bq2018 is small enough

to fit in the crevice between two Asize

cells or within the width of a

prismatic cell.