DS2441 View Datasheet(PDF) - Dallas Semiconductor -> Maxim Integrated
Part Name
Description
Manufacturer
DS2441 Datasheet PDF : 29 Pages
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DS2441
Charge and Discharge Current Accumulators. The Charge Current Accumulator (CCA) is a 16-bit,
read/write, up-only counter with 0.16C resolution which accumulates the total charging current the
battery pack has seen since the CCA was last reset. It is only updated when current through sense resistor
RSENS is positive; i.e., when the battery is being charged. Similarly, the Discharge Current Accumulator
(DCA) is a 16-bit, read/write, up-only counter with 0.16C resolution which accumulates the total
discharging current the battery pack has seen since the DCA was last reset. Each counter is incremented
at the rate of once per 0.16C, thus allowing six updates for each complete charge or discharge cycle.
Figure 6 shows the format of the CCA and DCA registers.
CCA AND DCA REGISTER FORMAT Figure 6
27 26 25 24 23 22 21 20 LSB
msb
(unit = 0.16C)
lsb
215 214 213 212 211 210 29 28 MSB
The ICA, CCA and DCA can be disabled by setting the ACC bit in the Configuration Register to logic 0.
When the accumulators are disabled, bytes 0, 2, 3, 4 and 5 of Page 2 become general purpose memory
available to the host system.
Current Accumulator Threshold. In order to allow accumulator adjustments for offset versus
resolution, two Configuration Register bits (TH1 and TH2) can be used to set a threshold on the measured
current below which the ICA, CCA and DCA won’t accumulate. When the threshold is set larger than
the maximum offset voltage of the internal A/D converter, the offset is effectively ignored by the
accumulators. A higher threshold setting offers maximum granularity and is recommended for high-
current use. A lower threshold setting is used to enhance long-term accuracy for light-duty battery use.
Table 5 enumerates the available threshold settings.
CURRENT ACCUMULATOR THRESHOLD SETTINGS Table 5
TH2
TH1
Threshold
0
0
None (default)
0
1
±2 LSB
1
0
±4 LSB
1
1
±8 LSB
DISCHARGE TERMINATION WARNING
The DS2441 continuously compares the ICA value with the alarm threshold stored in the read/write
Discharge Termination Warning (DTW) Register. If the ICA drops below the DTW threshold, the
DS2441 sets the DTW flag in the Status Register to provide a low battery warning to the host system.
The DTW flag is also set if the cell voltage falls below the discharge warning threshold VDW. The VDW
voltage threshold provides a back-up warning in case extreme operating conditions cause ICA inaccuracy.
The default DTW threshold value (0.000C) can be overwritten at any time. For a custom default value,
consult the factory. The DTW Register has the same format as the ICA (see Figure 5).
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