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3.5.1 Fuel Gauge
AB3100 supports the measurement of the current consumption/charging current in the U500 with a fuel
gauge block. By constantly integrating the current flowing into and out of the battery, the fuel gauge
block is used to determine the remaining battery capacity.
The function of the fuel gauge block is schematically described in (Fig.3-5-3). A sense resistor R_FGSENSE
is connected in series with the battery. The voltage across the resistor, equivalent to the current
entering/leaving the battery, is integrated using an ADC block.
1
2
3
4
B
A
T
T
_
G
N
2
0
1
2
R
5
1
9
R
1
/
4
W
0
0 .
2
5
1
%
Name
FGSENSEP
FGSENSEN
Copyright © 2009 LG Electronics. Inc. All right reserved.
Only for training and service purposes
Fig. 3-5-3. Fuel gauge block diagram
B
D
A
T
A
C
N
5
0
0
B
A
T
T
E
R
Y
C
O
N
N
E
C
T
O
R
H
S
B
C
3 -
P
T
2
5
1 -
4
E
N
Z
Y
0
0
1
7
7
0
1
D
V
B
A
T
F
G
S
+
o
u
t
e
a
s
a
d
i
f
f
e
r
e
n
t
i
a
l
p
a
i
r
R
5
2
1
0
F
G
- S
Fig. 3-5-4 The Schematic of the fuel gauge block
Type
Unused
Analog
VBAT
Analog
VBAT
Table 3-5-2. Fuel Gauge channel spec
S
C
L
K
S
D
A
T
B
D
A
T
A
F
G
S
+
C
5
2
7
4
7
p
F
G
- S
C
H
S
+
Description
Fuel gauge current sensing input positive
Fuel gauge current sensing input negative
- 59 -
3. TECHNICAL BRIEF
S
C
L
K
N
3
S
D
A
T
A
1
1
B
D
A
T
A
J
1
4
F
G
S
E
N
S
E
P
J
1
3
F
G
S
E
N
S
E
N
G
2
V
B
A
T
_
D
H
1
C
H
S
E
N
S
E
P
LGE Internal Use Only
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