DS2780 Maxim Integrated Products, DS2780 Datasheet - Page 12

• Manufacturer Part Number: DS2780
• Description: Stand-Alone Fuel Gauge IC
• Manufacturer: Maxim Integrated Products

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10°C slopes can be selected to optimize the model accuracy. A diagram of example battery cell model curves is
shown if Figure 11.
Figure 11. Cell Model Example Diagram
Full: The Full curve defines how the full point of a given cell depends on temperature for a given charge
termination. The charge termination method used in the application is used to determine the table values. The
DS2780 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.
Active Empty: The Active Empty curve defines the temperature variation in the empty point of the discharge profile
based on a high level load current (one that is sustained during a high power operating mode) and the minimum
voltage required for system operation. This load current is programmed as the Active Empty current (IAE), and
should be a 3.5s average value to correspond to values read from the Current register, and the specified minimum
voltage, or Active Empty voltage (VAE) should be a 220ms average to correspond to values read from the Voltage
register. The DS2780 reconstructs the Active Empty line from cell characteristic table values to determine the
Active Empty capacity of the battery at each temperature. Reconstruction occurs in one-degree temperature
increments.
Standby Empty: The Standby Empty curve defines the temperature variation in the empty point in the discharge
defined by the application standby current and the minimum voltage required for standby operation. In typical PDA
applications, Standby Empty represents the point that the battery can no longer support RAM refresh and thus the
standby voltage is set by the RAM voltage supply requirements. In other applications, Standby Empty can
represent the point that the battery can no longer support a subset of the full application operation, such as games
or organizer functions on a wireless handset. The standby load current and voltage are used for determining the
cell characteristics but are not programmed into the DS2780. The DS2780 reconstructs the Standby Empty line
from cell characteristic table values to determine the Standby Empty capacity of the battery at each temperature.
Reconstruction occurs in one-degree temperature increments.
100%
0°C
1
Derivative
[ppm / °C]
10°C
2
20°C
3
12 of 27
Standby
Empty
Active
Empty
FULL
30°C
4
40°C
Cell
Characterization
data points
DS2780 Stand-Alone Fuel Gauge IC