Linear Technology DC1812A Demo Manual page 6

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 size smaller than Q
LSB
ing the 16-bit accumulated charge register to underflow
before the battery is exhausted or overflow during charge.
In such cases, R should be sized according to the
SENSE
following relationship:
0.340mAh • 2
R
≤
SENSE
Q
BAT
6
16
/2 , caus-
BAT
16
• 50mΩ
Figure 5. Battery Gauge Tab
where Q is in mAh. Similarly, for applications with a
BAT
small battery but high maximum current the q
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
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:
50mΩ
q = 0.34mAh •
LSB
R
SENSE
can get
LSB
LSB
M
•
4096
dc1812af