2762A25 データシートの表示（PDF） - Maxim Integrated

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2762A25

High-Precision Li+ Battery Monitor With Alerts

Maxim Integrated 

DS2762 High-Precision Li+ Battery Monitor With Alerts

CURRENT MEASUREMENT

In active mode, the DS2762 continually measures the current flow into and out of the battery by measuring the

voltage drop across a current-sense resistor. The DS2762 is available in two configurations: 1) internal 25mW

current-sense resistor and 2) external user-selectable sense resistor. In either configuration, the DS2762 considers

the voltage difference between pins IS1 and IS2 (VIS = VIS1 - VIS2) to be the filtered voltage drop across the sense

resistor. A positive VIS value indicates current is flowing into the battery (charging), while a negative VIS value

indicates current is flowing out of the battery (discharging).

VIS is measured with a signed resolution of 12 bits. The current register is updated in two’s-complement format

every 88ms with an average of 128 readings. Currents outside the register range are reported at the range limit.

Figure 4 shows the format of the current register.

For the internal sense resistor configuration, the DS2762 maintains the current register in units of amps, with a

resolution of 0.625mA and full-scale range of no less than ±1.9A (see Note 7 on IFS spec for more details). The

DS2762 automatically compensates for internal sense resistor process variations and temperature effects when

reporting current.

For the external sense resistor configuration, the DS2762 writes the measured VIS voltage to the current register,

with a 15.625mV resolution and a full-scale ±64mV range.

Figure 4. Current Register Format

MSB—Address 0E

S 211 210 29 28 27 26 25

MSb

LSb

LSB—Address 0F

24 23 22 21 20 X X X

MSb

LSb

Units: 0.625mA for Internal Sense Resistor

15.625mV 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. Figure 5 shows the

format of the current accumulator.

When the internal sense resistor is used, the DS2762 maintains the current accumulator in units of amp-hours, with

a 0.25mAhrs resolution and full-scale ±8.2Ahrs range. When using an external sense resistor, the DS2762

maintains the current accumulator in units of volt-hours, with a 6.25mVhrs resolution and a full-scale ±205mVhrs

range.

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

Figure 5. Current Accumulator Format

MSB—Address 10

S 214 213 212 211 210 29 28

MSb

LSb

LSB—Address 11

27 26 25 24 23 22 21 20

MSb

LSb

Units: 0.25mAhrs for Internal Sense Resistor

6.25mVhrs for External Sense Resistor

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