DS2786BG+ Maxim Integrated Products, DS2786BG+ Datasheet - Page 8

• Manufacturer Part Number: DS2786BG+
• Description: IC FUEL GAUGE OCV-BASED 10-TDFN
• Manufacturer: Maxim Integrated Products

Specifications of DS2786BG+

• Function: Fuel, Gas Gauge/Monitor
• Battery Type: Lithium-Ion (Li-Ion), Lithium-Polymer (Li-Pol)
• Voltage - Supply: 2.5 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 10-TDFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

VOLTAGE MEASUREMENT
Battery voltage is measured at the V
1.22mV. The result is updated every 880ms and placed in the Voltage Register in two’s complement form. Voltages
above the maximum register value are reported as 7FFFh.
Figure 5. Voltage Register Format
The input impedance of V
order to support multiple-cell applications. The pack voltage should be divided by the number of series cells to
present a single-cell average voltage to the V
Every 1024th conversion, the ADC measures its input offset to facilitate offset correction to improve voltage
accuracy. Offset correction occurs approximately every 15 minutes. The resulting correction factor is applied to the
subsequent 1023 measurements. During the offset correction conversion, the ADC does not measure the V
signal. The voltage measurement just prior to the offset conversion is displayed in the voltage register. The OCV
algorithm automatically adjusts for the effects of the offset correction cycle.
AUXILARY INPUT MEASUREMENTS
The DS2786 has two auxiliary voltage measurement inputs, AIN0 and AIN1. Both are measured with respect to
V
identification resistors. Prior to the beginning of a measurement cycle on AIN0 or AIN1, the V
reference voltage in order to drive a resistive divider formed by a known resistor value, and the unknown resistance
to be measured. This technique delivers good accuracy at a reasonable cost, as it removes reference tolerance
from the error calculations. Measurements alternate between each input. Each auxiliary measurement is therefore
updated every 1760ms and placed in the corresponding AIN0 or AIN1 Register in two’s complement form.
Figure 6. Auxiliary Input Registers Format
SS
. These inputs are designed for measuring resistor ratios, particularly useful for measuring thermistor or pack
MSb
“S”: sign bit(s), “X”: reserved
AIN0
MSb
“S”: sign bit, “X”: reserved
AIN1
MSb
“S”: sign bit, “X”: reserved
S
S
S
2
2
2
11
10
10
MSB—Address 0Ch
MSB—Address 08h
MSB—Address 0Ah
2
2
2
10
9
9
IN
2
2
2
is sufficiently large (>15MΩ) to be connected to a high-impedance voltage divider in
9
8
8
2
2
2
8
7
7
IN
input with respect to V
2
2
2
7
6
6
IN
2
2
2
6
5
5
input.
LSb
LSb
LSb
2
2
2
5
4
4
8 of 22
MSb
MSb
MSb
SS
2
2
2
over a range of 0V to 4.5V and with a resolution of
4
3
3
2
2
2
DS2786 Stand-Alone OCV-Based Fuel Gauge
3
2
2
LSB—Address 0Dh
LSB—Address 09h
LSB—Address 0Bh
2
2
2
2
1
1
2
2
2
1
0
0
Units: V
Units: V
2
X
X
0
X
X
X
Units: 1.22mV
OUT
OUT
× 1/2047
× 1/2047
X
X
X
OUT
LSb
LSb
LSb
pin outputs a
X
X
X
IN