DS2790 Maxim Integrated Products, DS2790 Datasheet - Page 32

• Manufacturer Part Number: DS2790
• Description: Programmable 1-Cell Li-Ion Fuel Gauge and Protector
• Manufacturer: Maxim Integrated Products

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Accumulation Blanking
In order to avoid the accumulation of small positive offset errors over long periods, an offset blanking filter is
provided. The blanking filter is enabled by setting the OBEN bit in the ADC Configuration Register. When OBEN is
set, charge currents (positive values from the Current register) less than 62.5mV are not accumulated in the ACR.
The minimum charge current accumulated in the ACR is 4.167mA for RSNS = 0.015W.
Accumulation Bias
Systematic errors or an application preference can require the application of an arbitrary bias to the current
accumulation process. The Accumulation Bias value sets a user programmed positive or negative bias to the
current accumulation process. The accumulation bias value can be used to estimate battery currents that do not
flow through the sense resistor, estimate battery self-discharge, or correct for offset error accumulated in the ACR
register. The user programmed two’s compliment value is added to the ACR once per current sample. The bias
control is applied in 0.98mV increments over a ±125mV range. When using a 15mW sense resistor, the bias control
can be adjusted in 65.3mA increments over a ±8.33mA range. The Accumulation Bias bit field is located in the
upper byte of the ADC Configuration register.
Figure 14. Accumulation Bias Field
Voltage Measurement
The DS2790 continually measures the voltage between pins V
Voltage register is updated in two’s-complement format every 3.4ms with a resolution of 4.88mV. Voltages above
the maximum register value are reported as the maximum value.
Figure 15. Voltage Register Format
Temperature Measurement
The DS2790 uses an integrated temperature sensor to continually measure battery temperature. Temperature
measurements are updated in the Temperature register every 220ms in two’s-complement format with a resolution
of 0.125°C over a ±127°C range. The Temperature register format is shown in Figure 16.
4
MSb
“S”: sign bit
S
2
9
2
8
2
7
MSb
“S”: sign bit
Upper Byte of Word Address 600Ah
S
2
6
2
2
6
5
Word Address 6003h
2
2
5
4
DS2790 Programmable 1-Cell Li-Ion Fuel Gauge and Protector
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2
4
3
2
2
3
2
Units: 2
2
2
IN
2
1
0
and AV
= 0.98mV/Rsns
2
2
1
0
LSb
SS
2
X
0
over a 0.0V to V
X
Units: 2
X
0
X
= 4.88 mV
FS
LSb
X
range, and the