DC1652A
6
specific conditions in these boxes to facilitate their
control program development.
Clicking the
READ CONFIG
button can provide confir-
mation that the configuration change was actually
made. The six bytes read back should generally (un-
less special GPIO conditions exist) match the six bytes
sent and the PEC check bytes should be a match
(green PEC oval above the stack status display).
IMPORTANT NOTE
No configuration changes take effect until the
WRITE CONFIG button is clicked. A flashing
backlight serves as a reminder that this needs to be
performed.
Consult the LTC6803-2 data sheet for detailed informa-
tion concerning the variety of software configurable
functions possible. The following is a summary of
these functions:
Discharging individual cells,
Changing Over/Under voltage thresholds,
Preventing UV/OV interrupt flags from modifying
system operation through masking,
Systems status polling type; level or toggle polling,
Monitor comparator time interval,
GPIO pin functions -Inputs or Outputs,
10cell/12cell conversion mode,
Standby Mode-low current drain.
All of these can be implemented from the control panel
when selected from various points on the screen then
followed by a
WRITE CONFIG
button click.
6: READ TEMPERATURE
The LTC6803-2 has three ADC channels dedicated to
measuring temperature. The temperature indications
are for the internal die temperature of the LTC6803-2
and two externally connected thermistors. The display
returns a voltage measurement.
The internal die temperature sensor produces a voltag-
es that changes at a rate of 8mV/°C relative to absolute
zero. To convert the voltage reading to degrees Centi-
grade, divide the voltage by 8mV then subtract 273°C.
For example, 25°C is a nominal reading of 2.384V.
For external temperature measurements connect ther-
mistors across cells connector terminals J1-3 to J1-1
and J1-2 to J1-1. A thermistor with a 25°C value of
10K
Ω
will produce a half of V
REF
voltage reading at
25°C (approximately 1.55V). Any thermistor value may
be used but scaling the voltage measurement may re-
quire changing the values of resistors R55 and R56 on
the DC1652A circuit board.
To take a temperature reading simply click the
START
TEMP
command button to make the LTC6803-2 ADC
conversion followed by clicking the
READ TEMP
command button to download the data from the board
and display the voltage readings for temperature.
7: READ CELL VOLTAGES
The essential function of the LTC6802-2 is to measure
and report the voltage on each battery cell when com-
manded. Once again this is accomplished from the
control screen with two command button clicks. First
click on the
START CELL VOLT
button. This com-
mands an A/D conversion of all 12 cell-voltages.
NOTE:
All 12 cell-voltages are converted every time
regardless of the number of cells actually connected to
the LTC6803-2. Unused cell connections, if shorted
together, will return nominal voltage readings of 0.000
volts.
The actual cell voltage measurements are not displayed
until the
READ CELL VOLT
command button is clicked.
8: READ FLAGS
When any cell in a stack exceeds the programmed
over- or under-voltage threshold limit, one of two flag
bits is set in an internal register for that cell to serve as
a warning. This is simple feedback for battery charging
algorithms to know simply when to start or stop charg-
ing. To read the state of these warning flags at any
time is a simple click of the
READ FLAG
command
button. The Hex code for the three flag bytes appears
in the
FLAGS
section of the control panel at the top of
the screen.
One of the configuration options is to mask these flags
from appearing in the register bytes that are read from
the LTC6803-2. This feature can be used to either pre-
vent or allow these flags to report warnings to a con-