DS2438 Dallas Semiconducotr, DS2438 Datasheet - Page 8

• Manufacturer Part Number: DS2438
• Description: Smart Battery Monitor
• Manufacturer: Dallas Semiconducotr

THRESHOLD REGISTER FORMAT Table 6
The Charging Current Accumulator (CCA) is a two-byte nonvolatile read/write counter which represents
the total charging current the battery has encountered in its lifetime. It is only updated when current
through R
Accumulator (DCA) is a two-byte nonvolatile counter which represents the total discharging current the
battery has encountered over its lifetime.
The CCA and DCA can be configured to function in any of three modes: disabled, enabled with shadow-
to-EEPROM, and enabled without shadow-to-EEPROM. When the CCA and DCA are disabled (by
setting either the IAD bit or the CA bit in the Status/Configuration Register to “0”), the memory in page
07h is free for general purpose data storage. When the CCA and DCA are enabled (by setting both IAD
and CA to “1”), page 07h is reserved for these registers, and none of the bytes in page 07h should be
written to via the 1-Wire bus. When the CCA and DCA are enabled, their values are automatically
shadowed to EEPROM memory by setting the EE bit in the Status/Configuration Register to “1”. When
these registers are configured to shadow to EEPROM, the information will accumulate over the lifetime
of the battery pack and will not be lost when the battery becomes discharged. Shadow-to-EEPROM is
disabled when the EE bit is “0”. Table 7 illustrates the format of the CCA and DCA registers. Table 8
summarizes the modes of operation for ICA, CCA and DCA.
CCA/DCA REGISTER FORMAT Table 7
ICA/CCA/DCA MODES OF OPERATION Table 8
IAD Bit
0
1
1
1
SENS
, is positive; i.e., when the battery is being charged. Similarly, the Discharge Current
TH2
0
0
1
1
CA Bit
X
0
1
1
MSb
MSb
TH2
2
2
15
7
2
2
TH1
14
EE Bit
6
X
X
0
1
2
(unit = 15.625 mVHr)
2
13
5
0
2
2
12
4
0
TH1
0
1
0
1
Inactive
2
2
8 of 29
Active
Active
Active
11
3
ICA
0
2
2
10
2
0
2
2
1
9
0
CCA/DCA
LSb
Inactive
Inactive
2
2
Active
Active
LSb
0
8
0
MSB
LSB
THRESHOLD
None (default)
±2 LSB
±4 LSB
±8 LSB
CCA/DCA Copy-
to-EEPROM
Inactive
Inactive
Inactive
Active
DS2438