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dc1812af
DEMO MANUAL DC1812A
Quikeval interface
BATTERy GAuGE TAB
This tab contains controls to set up the battery gas gauge
and consists of two sections: User Input and Initialization.
user Input
For applications that have low current and a large battery, it
is possible to get a q
LSB
size smaller than Q
BAT
/2
16
, caus-
ing the 16-bit accumulated charge register to underflow
before the battery is exhausted or overflow during charge.
In such cases, R
SENSE
should be sized according to the
following relationship:
R
SENSE
≤
0.340mAh
•
2
16
Q
BAT
•
50m
Ω
Figure 5. Battery Gauge Tab
where Q
BAT
is in mAh. Similarly, for applications with a
small battery but high maximum current the q
LSB
can get
quite large with respect to the battery capacity causing a
loss in digital resolution in the accumulated charge register.
To address this, the LTC2943 includes a programmable
prescalar. Lowering the prescalar factor M reduces q
LSB
to better match the accumulated charge register to the
capacity of the battery. M can be chosen between 1 and
its default value of 4096. The charge LSB then becomes:
q
LSB
=
0.34mAh
•
50m
Ω
R
SENSE
•
M
4096
