Datasheet
30
www.ti.com
TSC2000
SBAS257
FIGURE 21. Battery Measurement Functional Block Diagram.
FIGURE 22. V
BAT1
Measurement Process.
FIGURE 23. V
BAT2
Measurement Process.
Host Writes
A/D Converter
Control Register
Start Clock
Battery Input 2
Done
Yes
No
Is Data
Averaging Done
Store Battery Input 2
in BAT2 Register
Power Down
A/D Converter
Power Up
A/D Converter
Power Up Reference
Convert
Battery Input 2
Issue Data Available
Power Down Reference
Turn Off Clock
Host Writes
A/D Converter
Control Register
Start Clock
Battery Input 1
Done
Yes
No
Is Data
Averaging Done
Store Battery Input 1
in BAT1 Register
Power Down
A/D Converter
Power Up
A/D Converter
Power Up Reference
Convert
Battery Input 1
Issue Data Available
Power Down Reference
Turn Off Clock
V
DD
V
BAT1
7.5kΩ
2.5kΩ
DC/DC
Converter
Battery
0.5V
to
6.0V
0.125V to 1.5V
2.7V
+
OPERATION—BATTERY MEASUREMENT
An added feature of the TSC2000 is the ability to monitor the
battery voltage on the other side of a voltage regulator (DC/
DC converter), as shown in Figure 21. The V
BAT1
input is
divided down by 4 so that an input range of 0.5V to 6.0V can
be measured. Because of the division by 4, this input range
would be represented as 0.125V to 1.5V to the A/D con-
verter.
The V
BAT2
input is divided down by 2, so it accommodates an
input range of 0.5V to 3.0V, which is represented to the A/D
converter as 0.25V to 1.5V. This smaller divider ratio allows
for increased resolution. Note that the V
BAT2
input pin can
withstand up to 6V, but this input will only provide accurate
measurements within the 0.5V to 3.0V range.
For both battery inputs, the dividers are ON only during the
sampling of the battery input, in order to minimize power
consumption.
Flowcharts which detail the process of making a battery input
reading are shown in Figures 22 and 23.
The time needed to make temperature, auxiliary, or battery
measurements is given by:
(7)
t 2.625 s + t N N
1
f
s
READING
REF
AVG BITS
CONV
=µ + • +µ
44.
where t
REF
is the reference delay time as given in Table XVII.