DS2788EVKIT+ Maxim Integrated, DS2788EVKIT+ Datasheet - Page 13

• Manufacturer Part Number: DS2788EVKIT+
• Description: Power Management IC Development Tools
• Manufacturer: Maxim Integrated
• Series: DS2788r

Specifications of DS2788EVKIT+

• Part # Aliases: 90-2788K+000

named full, active empty, and standby empty. Each
model curve is constructed with five line segments,
numbered 1 through 5. Above +50°C, the segment 5
model curves extend infinitely with zero slope, approxi-
mating the nearly flat change in capacity of Li+ cells at
temperatures above +50°C. Segment 4 of each model
curves originates at +50°C on its upper end and
extends downward in temperature to +25°C. Segment
3 joins with segment 2, which in turn joins with segment
1. Segment 1 of each model curve extends from the
junction with segment 2 to infinitely colder tempera-
tures. Segment slopes are stored as µVh ppm change
per °C. The two junctions or breakpoints that join the
segments (labeled TBP12 and TBP23 in Figure 12) are
programmable in 1°C increments from -128°C to
+25°C. They are stored in two’s complement format,
TBP23 at 7Ch, and TBP12 at 7Dh. The slope or deriva-
tive for segments 1, 2, 3, and 4 are also programmable.
Figure 12. Cell Model Example Diagram
100%
______________________________________________________________________________________
SEGMENT 1
DERIVATIVE
(ppm/°C)
Stand-Alone Fuel-Gauge IC with
TBP12
SEGMENT 2
ACTIVE
EMPTY
TBP23
Full: The full curve defines how the full point of a given
cell stack depends on temperature for a given charge
termination. The charge termination method used in the
application is used to determine the table values. The
DS2788 reconstructs the full line from cell characteristic
table values to determine the full capacity of the battery
at each temperature. Reconstruction occurs in one-
degree temperature increments. Full values are stored
as ppm change per °C. For example, if a cell had a
nominal capacity of 1214mAh at +50°C, a full value of
1199mAh at +25°C, and 1182mAh at 0°C (TBP23), the
slope for segment 3 would be:
1 LSB of the slope registers equals 61ppm so the full
segment 3 slope register (location 0x6Dh) would be
programmed with a value of 0x09h. Each Slope register
has a dynamic range 0ppm to 15555ppm.
STANDBY
FULL
SEGMENT 3
EMPTY
((1199mAh - 1182mAh) / (1214mAh / 1M)) /
LED Display Drivers
+25°C
(25°C - 0°C) = 560ppm/°C
SEGMENT 4
CHARACTERIZATION
CHARACTERIZATION
CELL
CELL
+50°C
SEGMENT 5
13