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.