DS2751

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CURRENT MEASUREMENT

In the active mode of operation, the DS2751 continually measures the current flow into and out of the

battery by measuring the voltage drop across a current-sense resistor. The DS2751 is available in two

configurations: 1) internal 25m

W current-sense resistor, and 2) external user-selectable sense resistor. In

battery (discharging).

format every 88ms with an average of 128 measurements. Currents outside the range of the register are

reported at the limit of the range. The format of the Current Register is shown in Figure 3.

For the internal sense resistor configuration, the DS2751 maintains the Current Register in units of amps,

with a resolution of 0.625mA and full-scale range of no less than

details). The DS2751 automatically compensates for internal sense-resistor process variations and

temperature effects when reporting current.

Register in units of volts, with a resolution of 15.625

mV and a ±64mV full-scale range.

Figure 3. CURRENT REGISTER FORMAT

MSB—Address 0E

LSB—Address 0F

S

X

X

X

MSb

LSb

MSb

LSb

Units: 0.625mA for internal sense resistor

15.625

mV for external sense resistor

CURRENT ACCUMULATOR

The Current Accumulator facilitates remaining capacity estimation by tracking the net current flow into

and out of the battery. Current flow into the battery increments the Current Accumulator, while current

flow out of the battery decrements it. Data is maintained in the Current Accumulator in two’s-

complement format. The format of the Current Accumulator is shown in Figure 4.

When the internal sense resistor is used, the DS2751 maintains the Current Accumulator in units of amp-

hours, with a resolution of 0.25mAhrs and a

±8.2Ahrs full-scale range. When using an external sense

resistor, the DS2751 maintains the Current Accumulator in units of volt-hours, with a resolution of

6.25

mVhrs and a ±205mVhrs full-scale range.

The Current Accumulator is a read/write register that can be altered by the host system as needed.