Fuel Gauge - LG U400 Service Manual

3.4.11 Fuel Gauge

AB2010 supports the measurement of the current consumption/charging current in the U8100 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.3-4-14). 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.
Fig. 3-4-13. The analog front-end of the fuel gauge block
VBAT
Name Type
FGSENSE+ Analog
FGSENSE- Analog
DACDAT
VBATI
DACCLK
DACSTR
replace 2012size
R522
0.025
0.025 ohm
VBUS
C520 C521
47p 47p
Fig. 3-4-14 The Schematic of the fuel gauge block
Unused
VBAT
VBAT
Table 3-4-7. Fuel Gauge channel spec
- 67 -
C9
DAC_DAT
A10
DAC_CLK
B10
DAC_STR
R523 0 M12
VBAT_B
A8
R525 0
VBAT_F
C512 C513
0.1u 4.7u
1608 10V
E9
MOD1
F11
FGSENSE+
F12
FGSENSE-
D501 CUS02 F2
VBUS
R535 0 F3
MOD_USB
R536
E1
VBAT_D
0
C522
0.1u
Description
Fuel gauge current sensing input positive
Fuel gauge current sensing input negative
3. Technical Brief