STC3105

Functional description

Doc ID 022198 Rev 1

11/23

6.4

Coulomb counter

The coulomb counter is used to track the state-of-charge of the battery when the battery is

charging or discharging at a high rate. Each result of current conversion is accumulated into

a 28-bit accumulator. The upper 16 bits of the accumulator are added to the SOC base

register to provide the current state-of-charge (SOC) in the charge register. The system

controller can control the coulomb counter, set the SOC base register value and read the

Figure 4.

Coulomb counter block diagram

When using an external 30 m

Ω sense resistor, the 28-bit accumulator results in a coulomb

counter capacity of approximately +/- 7300 mA.h. The upper 16 bits used for the charge

register give a resolution of 0.2 mA.h.

6.5

Alarm output

The ALM pin provides an alarm signal in case of low battery condition. The output is an

open drain, and an external pull-up resistor may be needed in the application. Writing the

IO0DATA bit to 0 forces the ALM output low; writing the IO0DATA bit to 1 lets the ALM output

reflect the battery condition. Reading the IO0DATA bit gives the state of the ALM pin.