Rainbow Electronics DS2784 - Manual (Page 19)

DS2784: 1-Cell Stand-Alone Fuel Gauge IC with Li+ Protector and SHA-1 Authentication
model curve are stored in the cell parameter EEPROM block as ppm/°C. The breakpoint temperatures of each
segment are stored there also (see Application Note 3584: Storing Battery Fuel Gauge Parameters in DS2780 for
more details on how values are stored). An example of data stored in this manner is shown in Table 6.
able 6. Example Cell Characterization Table (Normalized to +40°C) T
19 of 38
anufacturer’s Rated Cell Capacity: 1000mAh M
Charge Voltage: 4.2V
Termination Current: 50mA
Active Empty (V): 3.0V Active Empty (I): 300mA
Sense Resistor: 0.020
Ω
TBP12 TBP23 TBP34
Segment
s Breakpoint
-12
°C 0°C 18°C
+40
N
Seg. 1 Seg. 2 Seg. 3 Seg. 4
°C
ominal
(mAh)
ppm/
°C
ppm/
°C
ppm/
°C
ppm/
°C
Full 1051 3601 3113 1163 854
Active Empty 2380 1099 671 305
Standby Empty 1404 427 244 183
Figure 4. Lookup Function Diagram
PPLICATION PARAMETERS
everal application parameters are needed to detect the full and empty
ense Resistor Prime (R
SNSP
[1/
Ω])—R
SNSP
stores the value of the sense resistor for use in computing the absolute
R
SNSP
= 1/R
SNS
(units of mhos; 1/
Ω)
harge Voltage (VCHG) —VCHG stores the charge voltage threshold used to detect a fully charged state. The
* See Result Registers section for a description of these registers.
CELL MODEL
PARAMETERS
(EEPROM)
TEMPERATURE
LOOKUP
FUNCTION
FULL(T)
*
AE(T)
*
SE(T)
*
A
In addition to cell model characteristics, s
points, as well as calculate results in mAh units.
S
capacity results. The resistance is stored as a 1-byte conductance value with units of mhos (1/
Ω). R
SNSP
supports
resistor values of 1 Ω to 3.922mΩ. R
SNS
is located in the parameter EEPROM block.
C
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.