ds2782 Maxim Integrated Products, Inc., ds2782 Datasheet - Page 16

• Manufacturer Part Number: ds2782
• Description: Ds2782 Stand-alone Fuel Gauge Ic
• Manufacturer: Maxim Integrated Products, Inc.

DS2782: Standalone Fuel Gauge IC
When an empty condition is detected (AEF or LEARNF set), the ACR adjustment is conditional. If AEF is set and
LEARNF is not, then the Active Empty Point was not detected and the battery is likely below the Active Empty
capacity of the model. The ACR is set to the Active Empty model value only if it is greater than the Active Empty
model value. If LEARNF is set, then the battery is at the Active Empty Point and the ACR is set to the Active Empty
model value.
Full Detect
Full detection occurs when the Voltage (VOLT) readings remain continuously above the VCHG threshold for the
period between two Average Current (IAVG) readings, where both IAVG readings are below IMIN. The two
consecutive IAVG readings must also be positive and non-zero. This ensures that removing the battery from the
charger does not result in a false detection of full. Full Detect sets the Charge to Full (CHGTF) bit in the Status
register.
Active Empty Point Detect
Active Empty Point detection occurs when the Voltage register drops below the VAE threshold and the two
previous Current readings are above IAE. This captures the event of the battery reaching the Active Empty point.
Note that the two previous Current readings must be negative and greater in magnitude than IAE, that is, a larger
discharge current than specified by the IAE threshold. Qualifying the Voltage level with the discharge rate ensures
that the Active Empty point is not detected at loads much lighter than those used to construct the model. Also,
Active Empty must not be detected when a deep discharge at a very light load is followed by a load greater than
IAE. Either case would cause a learn cycle on the following charge to full to include part of the Standby capacity in
the measurement of the Active capacity. Active Empty detection sets the Learn Flag (LEARNF) bit in the Status
register.
RESULT REGISTERS
The DS2782 processes measurement and cell characteristics on a 3.5s interval and yields seven result registers.
The result registers are sufficient for direct display to the user in most applications. The host system can produce
customized values for system use, or user display by combining measurement, result and User EEPROM values.
FULL(T) [ ]: The Full capacity of the battery at the present temperature is reported normalized to the 40°C Full
value. This 15-bit value reflects the cell model Full value at the given temperature. FULL(T) reports values between
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100% and 50% with a resolution of 61ppm (precisely 2
). Though the register format permits values greater than
100%, the register value is clamped to a maximum value of 100%.
Active Empty, AE(T) [ ]: The Active Empty capacity of the battery at the present temperature is reported
normalized to the 40°C Full value. This 13-bit value reflects the cell model Active Empty at the given temperature.
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AE(T) reports values between 0% and 49.8% with a resolution of 61ppm (precisely 2
).
Standby Empty, SE(T) [ ]: The Standby Empty capacity of the battery at the present temperature is reported
normalized to the 40°C Full value. This 13-bit value reflects the cell model Standby Empty value at the current
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temperature. SE(T) reports values between 0% and 49.8% with a resolution of 61ppm (precisely 2
).
Remaining Active Absolute Capacity (RAAC) [mAh]: RAAC reports the capacity available under the current
temperature conditions at the Active Empty discharge rate (IAE) to the Active Empty point in absolute units of milli-
amp-hours. RAAC is 16 bits.
Remaining Standby Absolute Capacity (RSAC) [mAh]: RSAC reports the capacity available under the current
temperature conditions at the Standby Empty discharge rate (ISE) to the Standby Empty point capacity in absolute
units of milli-amp-hours. RSAC is 16 bits.
Remaining Active Relative Capacity (RARC) [%]: RARC reports the capacity available under the current
temperature conditions at the Active Empty discharge rate (IAE) to the Active Empty point in relative units of
percent. RARC is 8 bits.
Remaining Standby Relative Capacity (RSRC) [%]: RSRC reports the capacity available under the current
temperature conditions at the Standby Empty discharge rate (ISE) to the Standby Empty point capacity in relative
units of percent. RSRC is 8 bits.
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