DS2784 Maxim Integrated Products, DS2784 Datasheet - Page 19

• Manufacturer Part Number: DS2784
• Description: 1-Cell Stand-Alone Fuel Gauge IC
• Manufacturer: Maxim Integrated Products

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Table 6. Example Cell Characterization Table (Normalized to +40°C)
Manufacturer’s Rated Cell Capacity: 1000mAh
Charge Voltage: 4.2V
Active Empty (V): 3.0V
Sense Resistor: 0.020Ω
Segment
Breakpoints
Full
Active Empty
Standby Empty
Figure 4. Lookup Function Diagram
APPLICATION PARAMETERS
In addition to cell model characteristics, several application parameters are needed to detect the full and empty
points, as well as calculate results in mAh units.
Sense Resistor Prime (R
capacity results. The resistance is stored as a 1-byte conductance value with units of mhos (1/Ω). R
resistor values of 1Ω to 3.922mΩ. R
Charge Voltage (VCHG)—VCHG stores the charge voltage threshold used to detect a fully charged state. The
voltage is stored as a 1-byte value with units of 19.5mV and can range from 0V to 4.978V. VCHG should be set
marginally less than the cell voltage at the end of the charge cycle to ensure reliable charge termination detection.
VCHG is located in the parameter EEPROM block.
Minimum Charge Current (IMIN)—IMIN stores the charge current threshold used to detect a fully charged state. It
is stored as a 1-byte value with units of 50μV (IMIN x R
20mΩ, IMIN can be programmed from 0mA to 637.5mA in 2.5mA steps. IMIN should be set marginally greater than
*
See Result Registers section for a description of these registers.
TEMPERATURE
Nominal
PARAMETERS
TBP12
CELL MODEL
(mAh)
+40°C
-12°C
1051
(EEPROM)
SNSP
DS2784: 1-Cell Stand-Alone Fuel Gauge IC with Li+ Protector and SHA-1 Authentication
[1/Ω])—R
ppm/°C
TBP23
Seg. 1
SNS
3601
2380
1404
0°C
R
is located in the parameter EEPROM block.
SNSP
SNSP
stores the value of the sense resistor for use in computing the absolute
= 1/R
ppm/°C
TBP34
Seg. 2
18°C
3113
1099
427
Termination Current: 50mA
Active Empty (I): 300mA
SNS
19 of 37
FUNCTION
LOOKUP
(units of mhos; 1/Ω)
SNS
ppm/°C
Seg. 3
) and can range from 0 to 12.75mV. Assuming R
1163
671
244
ppm/°C
Seg. 4
854
305
183
FULL(T)
SE(T)
AE(T)
*
*
*
SNSP
supports
SNS
=