DS2786BG+T&R Maxim Integrated Products, DS2786BG+T&R Datasheet - Page 9

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

Specifications of DS2786BG+T&R

• 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

Battery voltage is measured at the V
to 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 is the Voltage Register format.
The input impedance of V
(> 15MΩ) to be connected to a high-impedance volt-
age-divider in order to support multiple-cell applica-
tions. 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
15min. The resulting correction factor is applied to the
subsequent 1023 measurements. During the offset-cor-
rection conversion, the ADC does not measure the V
signal. The voltage measurement just prior to the offset
Figure 5. Voltage Register Format
Figure 6. Auxiliary Input Registers Format
MSB
“S”: SIGN BIT, “X”: RESERVED
AIN0
MSB
“S”: SIGN BIT, “X”: RESERVED
AIN1
MSB
“S”: SIGN BIT, “X”: RESERVED
SS
S
S
S
over a 0 to 4.999V range and with a resolution of
2
2
2
11
10
10
IN
2
2
2
10
input.
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_______________________________________________________________________________________
MSB—ADDRESS 0Ch
Voltage Measurement
2
2
2
9
8
8
MSB—ADDRESS 0Ah
MSB—ADDRESS 08h
Stand-Alone OCV-Based Fuel Gauge
IN
2
2
2
8
7
7
is sufficiently large
IN
2
2
2
input with respect
7
6
6
2
2
2
6
5
5
LSB
LSB
LSB
2
2
2
5
4
4
IN
conversion is displayed in the Voltage Register. The
OCV algorithm automatically adjusts for the effects of
the offset-correction cycle.
The DS2786B has two auxiliary voltage-measurement
inputs, AIN0 and AIN1. Both are measured with respect
to V
tor ratios, particularly useful for measuring thermistor or
pack identification resistors. Prior to the beginning of a
measurement cycle on AIN0 or AIN1, the V
puts a 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 calcula-
tions. 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 shows the
Auxiliary Input Registers format.
MSB
MSB
MSB
2
2
2
SS
4
3
3
. These inputs are designed for measuring resis-
Auxilary Input Measurements
2
2
2
3
2
2
2
2
2
2
1
1
LSB—ADDRESS 0Dh
LSB—ADDRESS 09h
LSB—ADDRESS 0Bh
2
2
2
1
0
0
2
X
X
0
UNITS: V
UNITS: V
X
X
X
UNITS: 1.22mV
OUT
OUT
OUT
X
X
X
× 1/2047
× 1/2047
pin out-
LSB
LSB
LSB
X
X
X
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