DS2760 Dallas Semiconducotr, DS2760 Datasheet - Page 8

• Manufacturer Part Number: DS2760
• Description: High Precision Li-Ion Battery Monitor
• Manufacturer: Dallas Semiconducotr

Summary. All of the protection conditions described above are OR'ed together to affect the
outputs.
CURRENT MEASUREMENT
In the Active Mode of operation, the DS2760 continually measures the current flow into and out of the
battery by measuring the voltage drop across a current sense resistor. The DS2760 is available in two
configurations: (1) internal 25 m current sense resistor, and (2) external user-selectable sense resistor. In
either configuration, the DS2760 considers the voltage difference between pins IS1 and IS2 (V
V
flowing into the battery (charging), while a negative V
battery (discharging). Note than when an external sense resistor is used, one end of the resistor must be
wired directly to VSS (the negative terminal of the cell) for proper operation of the current measurement
circuitry.
V
two’s-complement format. 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 4.
For the internal sense resistor configuration, the DS2760 maintains the Current Register in units of Amps,
with a resolution of 0.625 mA and full scale range of no less than 1.8A (see Note 7 on I
details). The DS2760 automatically compensates for internal sense resistor process variations and
temperature effects when reporting current.
For the external sense resistor configuration, the DS2760 writes the measured V
Register, with a resolution of 15.625 V and a full scale range of 64 mV.
CURRENT REGISTER FORMAT – Figure 4
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.
complement format. The format of the Current Accumulator is shown in Figure 5.
IS2
IS
) to be the filtered voltage drop across the sense resistor. A positive V
is measured with a signed resolution of 12-bits. Measurements are placed in the Current Register in
DC
CC
MSb
S
= (Undervoltage) or (Overcurrent, EITHER Direction) or (Short Circuit) or
= (Overvoltage) or (Overcurrent, Charge Direction) or (Protection Register bit CE = 0) or
2
(Protection Register bit DE = 0) or (Sleep Mode)
(Sleep Mode)
11
MSB—Address 0E
2
10
2
9
2
8
2
7
2
6
Data is maintained in the Current Accumulator in two’s-
LSb
2
5
8 of 25
MSb
IS
2
4
value indicates current is flowing out of the
2
3
Units: 0.625 mA for internal sense resistor
LSB—Address 0F
2
2
15.625 V for external sense resistor
2
1
IS
2
0
value indicates current is
IS
voltage to the Current
X
X
FS
spec for more
LSb
CC
X
IS
= V
and
DS2760
IS1
DC
–