BQ2060A_15 Datasheet, PDF (52/61 Pages) Texas Instruments – SBS v1.1-Compliant Gas Gauge IC

bq2060A
SLUS500D – OCTOBER 2001 – REVISED OCTOBER 2011
www.ti.com
The bq2060A first computes the node voltages Vn1, Vn2, Vn3, and Vn4. The node voltages are inputs to the
voltage dividers to the VCELL₁ through VCELL₄ input pins of the bq2060A. The bq2060A computes node
voltages to calculate the five reported voltages by the bq2060A: Voltage(), VCELL1, VCELL2, VCELL3, and
VCELL4.
An ADC Voltage Gain factor of 20,000 is the nominal value when using the recommended cell-voltage division
ratios of 16:1 on the VCELL₄ and VCELL₃ inputs and 8:1 on the VCELL₂ and VCELL₁ inputs. The bq2060A
subtracts the voltage across the sense resistor from the measurements so that the reported voltages reflect the
cell-stack voltages only.
The bq2060A compute the node voltages as follows:
ƪ ƫ ƪ ƫ Vn1 +
VCELL 32768
1250
)
ADC
Offset
ADC Voltage Gain
65536
(27)
ƪ ƫ Vn2 +
VCELL 32768
1250
)
ADC
Offset
ƪ ƫ ADC Voltage Gain ) 8 Cell 2 CalibrationFactor
65536
(28)
ƪ ƫ Vn3 +
VCELL 32768
1250
)
ADC
Offset
ƪ ƫ ƪ ƫ ADC Voltage Gain ) 8 Cell 3 CalibrationFactor
65536
2
65536
(29)
ƪ ƫ Vn4 +
VCELL 32768
1250
)
ADC
Offset
ƪ ƫ ƪ ƫ ADC Voltage Gain ) 8 Cell 4 CalibrationFactor
65536
2
65536
(30)
Note: With LCC1 – LCC0 = 00, Cell 4 Calibration Factor = 0.
ADC Offset adjusts the ADC reading for voltage and current measurements. ADC Offset is a signed 8-bit value
that cancels offset present in the circuit with no potential or current flow. ADC Offset is typically set between –20
and 20.
The bq2060A uses the computed node voltages to calculate the reported voltages. It does not compute reported
cell voltages greater than the selected number of nodes. If no individual cell voltages are to be measured,
LCC1 – LCC0 should be set to 00 and the top of the battery stack should be connected to a voltage divider to
the VCELL4 input.
The bq2060A computes the reported voltages as follows:
• Voltage() = Vn4 (LCC1 – LCC0 = 11 or 00) – V_sr
• Voltage() = Vn3 (LCC1 – LCC0 = 10) – V_sr
• Voltage() = Vn2 (LCC1 – LCC0 = 01) – V_sr
• VCELL4 = Vn4– Vn3
• VCELL3 = Vn3– Vn2
• VCELL2 = Vn2– Vn1
• VCELL1 = Vn1– V_sr
Current
The bq2060A scales Current() to mA units by the 16-bit value ADC Sense Resistor Gain in EE 0x68–0x69.
Adjusting ADC Sense Resistor Gain from its nominal value provides a method to calibrate the current readings
for variances in the ADC gain, internal voltage reference, and sense resistor value. The bq2060A calculates
Current() by
52
Submit Documentation Feedback
Product Folder Link(s): bq2060A
Copyright © 2001–2011, Texas Instruments Incorporated