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STC3117

Functional description

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6.4

Current monitoring

The battery average current is monitored and is used in conjunction with a timer to

implement a battery relaxation timer.

Battery relaxation timer

The battery relaxation timer is used to detect a light-load, low-power condition.

The REG_CMONIT_COUNT register is an 8-bit, read-only counter that is incremented

every 4 s when the average current is inside a window defined by positive and negative

thresholds set by the REG_CURRENT_THRES register, and decremented every 500 ms

when the current is outside the thresholds.

When the counter reaches its maximum value set by the REG_CMONIT_MAX register, a

low-power condition is reported to the mixed mode algorithm causing VM mode to be used.

When the counter reaches its minimum value (0), a high-power condition is reported and CC

mode is used.

The REG_CMONIT_MAX register sets the maximum value of the counter. With the default

value (120 dec), the counter provides an 8-minute delay when switching from CC to VM

mode and a 1-minute delay when switching from VM to CC mode.

The REG_CURRENT_THRES register is an 8-bit R/W register set by the gas gauge

applicable for both positive and negative thresholds). Bit 7 of REG_CURRENT_THRES is

reserved and must be set to zero for operation of the current monitoring counter as a

relaxation timer. The LSB value of the REG_CURRENT_THRES is 47.04 µV and provides a

range of 0 to 6 mV.

It is possible to set the counter to zero or the maximum value using the FORCE_CC and

FORCE_VM bits in the REG_MODE register. These bits are self-clearing.