0BDESCRIPTION
Evaluation circuit DC1651A is a Battery Monitoring
System to demonstrate the functional operation of the
LTC6803-1
integrated circuit. The basic operation and
features of this demo board are the same as the
DC1331 for the LT6802-1, including the ability to
dai-
sy-chain up to 10 devices with built-in board-to-board
ribbon-cable interconnects and selectively apply resis-
tive loading to any cell for purposes of “Passive Ba-
lancing.”
1BLTC6803-1 NEW FEATURES
Pin compatible upgrade to LT6802-1 designs.
Robust daisy chain SPI common-mode immunity.
Packet Error Checking on command writes.
6X lower standby current.
Active pullup on S pins.
Additional diagnostic features.
2BDC1651A DEMO FEATURES
Controllable discharging for Passive Balancing.
Protection circuitry for IC and external discharge
transistors during hot plugging of cells.
Graphical User Interface (GUI) screen for demon-
stration of new features and program code devel-
opment.
DC1651A
June 18, 2010
LTC6803-1 Battery Monitor
HARDWARE/SOFTWARE USERS GUIDE
CELLS CONNECTOR
DISCHARGE SWITCHES
BOTTOM
PORT
LTC6803-1
TOP
PORT
CONFIGURATION JUMPERS
DC1651A
2
3BGETTING STARTED WITH ONE BOARD CONNECTED
5B
SINGLE BOARD CONNECTION TO PC AND GUI
Step 1.
Set jumpers on DC1651A to the default posi-
tions indicated in Table 1.
6B
TABLE 1. JUMPER FUNCTIONS
JUMPER FUNCTION DEFAULT
POSITION
ACTIVE POSITION GROUND POSITION
J4
Top of Stack (TOS) Active Indicates that the cells monitored by the
board are at the top of the battery stack. Data
is not transferred in or out of the Top Port of
this board.
Allows data to be passed to and from both the
Top and Bottom Ports of the board.
J6
General Purpose I/O
(GPIO1)
Active Output connected to pull-up resistor to Vreg.
Can be programmed as an input or an output.
Forced to a logic low level.
J7
General Purpose I/O
(GPIO2)
Active Output connected to pull-up resistor to Vreg.
Can be programmed as an input or an output.
Forced to a logic low level.
J8
Voltage Mode (VMOD) Active Bottom SPI port is configured as normal TTL
voltage level inputs and outputs. Required
setting for the board on the bottom of the
battery cell stack.
A 5K
:
PULL-UP RESISTOR
MUST BE CONNECTED FROM THE SDO
OUTPUT LINE (CONNECTOR J2, PIN 5) TO
THE LOGIC POWER RAIL OF THE CIRCUIT
DRIVING THE BOTTOM SPI PORT (SEE
TEXT).
Bottom Port is configured as a current inputs
and outputs. Required setting for all boards on
a cell stack above the bottom board.
Step 2.
Connect DC590B Quick Eval USB cable to
PC/Laptop USB port. Connect ribbon cable from
DC590B to the Bottom Port of DC1651A (J2).
Make sure that the driver for DC590B has been
downloaded from
HU
www.linear.com
UH
and installed on
the computer. This can be verified by running
Quick Eval and seeing the message that there is a
missing module for this board type. Close the
Quick Eval program and instead launch the control
program:
LTC6803-1-3_GUI_Vxx_yyyymmdd.exe
When the DC590B Quick Eval board recognizes the
String ID code from the DC1651A board, the pro-
gram will open and present the control screen.
This sometimes requires two launches of the GUI
program to properly initialize.
A DC590B board has the required pull-up resistor
to the SDO line already connected.
If a system
other than DC590 is driving the bottom port
(which must be set to Voltage Mode) must have a
5K
:
pull-up resistor added between the SDO line
(J2, PIN 5) and the 3V/5V logic supply rail of the
driving system.
This pull-up resistor was not add-
ed to the DC1651 because it cannot be present
when the port is configured for current mode op-
eration on a multiple board monitor of a stack of
cells.
Step 3.
Connect the cells to be monitored to the cells
connector J1. This connector is in two pieces. The
setscrew piece can be unplugged to make it safer
to attach wiring from a four to twelve cell battery
stack. The LTC6803-1 is intended to measure from
four to twelve individual cells with a total stack vol-
tage of 10V to 50V.
With fewer than 12 cells to be monitored, the bot-
tom cell of the stack should always be connected
as Cell 1 between terminals J1-5(+cell contact) and
J1-4(-cell contact). Terminals J1-4, and J1-1 are
DC1651A
3
the ground reference point for the battery cell stack
and for the DC1651A board. The second cell on the
stack connects between terminals J1-6(+cell con-
tact) and J1-5(-cell contact). All higher numbered
terminals on J1 not used for cell connections may
be shorted together. The V+ positive supply for the
DC1651A is the potential at terminal J1-16 and
therefore must connect to the top of the battery
stack. Figure 1 illustrates a connection for fewer
than 12 cells.
7B
SPECIAL NOTE FOR DEMONSTRATION PURPOSES
DC1651A and the GUI program are useful to serve as a
demonstration tool to highlight the features of the
LTC6803-1. If actual battery cells are not available, a
series string of 150
:
resistors connected between
each of the J1 connector terminals can be used in-
stead. Each resistor will serve as a cell voltage. A lab
power supply voltage of 10V to 50V can be connected
across the resistor string between terminals J1-16(+)
and J1-4(-).
When using resistors instead of cells, the discharge
indicating LEDs on the DC1651A board will not light
due to limited available current.
Step 4.
Apply power.
Inserting the setscrew piece into connector J1 will
apply power to the board from the battery cell stack.
For the demo set up simply turn on the lab power
supply preset to a voltage between 10V and 50V.
Figure 1. Connection of four cells (cell voltages at least 2.5V)
DC1651A
4
THE CONTROL PROGRAM
8B
THE GRAPHICAL USER INTERFACE (GUI) SCREEN
Figures 2 shows the control panel that appears on the
computer screen. The DC1651A board must be con-
nected to the DC590 interface card for the program to
open. The control screen will close if any of the boards
are disconnected. Controls on this panel are used to
communicate with the LTC6803-1. Commands are is-
sued and information is retrieved and displayed on this
screen. This panel is useful not only for demonstrating
the operation of the LTC6803-1, but also for software
developers to observe the Hex codes exchanged with
the device.
The control screen makes good use of color to provide
cell status and operating conditions at a glance. White
indicates non-existent or stale data. A step by step
procedure for one board connected to a stack of cells
follows to explain the operation of the control panel.
Sections are highlighted for each procedure.
Figure 2. GUI Control Panel Start-up Screen
DC1651A
5
4BOPERATING THE CONTROL
SCREEN
9B
FIRST THINGS FIRST
Figure 2 is the initial start-up screen that appears when
the program is launched and the Quick Eval interface
card recognizes that the DC1651A board is connected.
Once power is supplied to the board from a stack of
cells or a power supply, the communication between
the PC and the board can be checked.
10B
1: READ CONFIGURATION
Click the command button labeled
READ CONFIG.
If all
is properly connected and operating the start-up de-
fault configuration of the LTC6803-1 will be read from
the board. The Hex codes for the six bytes of configu-
ration setting will appear in the
CONFIGURATION
REGISTERS
section in the boxes labeled
CONFIGURATION READ FROM LTC6803-1
. The initial
configuration bytes should be 0xE0 for register 0 and
0x00 for the other five bytes.
This default configura-
tion is the standby mode for the LTC6803-1. To ena-
ble the device and begin taking cell voltage mea-
surements, a CDC (Comparator Duty Cycle) setting
other than Standby must be selected from the SET
I/O MODE set CDC selection box at the bottom of the
GUI screen. Once chosen, a WRITE CONFIG com-
mand must be executed.
In addition the LTC6803-1 calculates a Packet Error
Code, PEC, and appends it to the data stream each
time it sends out data. For the six bytes sent by this
command and received by the GUI, the control pro-
gram calculates a PEC in the same manner. This byte
is compared with the appended receive byte to check
that the data transmission was properly executed. The
Received PEC byte and the calculated PEC from the
received data are displayed in the top section labeled
PACKET ERROR CODE
and both bytes should match.
The oval located at the top of the color-coded status
panel for the one board will turn green if the PEC bytes
match. Data transmission errors will produce red
warning indications if the PEC bytes do not match.
There is also a display of the PEC that was sent with
the most recent command to the LTC6803-1, which
had to match an internally calculated value to be ac-
cepted as a valid command.
11B
2: WRITE CONFIGURATION
Nothing is changed in the LTC6803-1 until the Write
Configuration command is executed. Clicking the
WRITE CONFIG
command button does this. When the
command is sent, the six Hex bytes shown in the
CONFIGURATION REGISTERS
section in the boxes
labeled
CONFIGURATION WRITTEN TO LTC6803
will
become
bold
type. Software developers can note the
exact hex values required by the LTC6803-1 for specif-
ic conditions in these boxes to facilitate their control
program development.
Clicking the
READ CONFIG
button can see confirma-
tion that the configuration change was actually made.
The six bytes read back should match the six bytes
sent and the PEC/CRC check bytes should be a match
(green PEC oval on stack display).
When any configuration information is changed on the
screen the
WRITE CONFIG
command button will be
back-lit illuminated. This serves as a reminder that this
command still needs to be executed.
12B
IMPORTANT NOTE
32B
No configuration changes take effect until the
WRITE CONFIG button is clicked. The GUI provides
a periodic background command so that watchdog
does not trigger CDC reset back to 0.
DC1651A
6
13B
3: PROGRAM THE CELL MONITORING VOLTAGE
THRESHOLDS
In the section labeled
SET VOLTAGE LIMITS
click on
the boxes and enter voltage values for the over-voltage
and under-voltage thresholds required for the cells be-
ing monitored. The voltage value entered will be
rounded to the actual value used by the LTC6803-1
and displayed in the box. The voltage ranges for these
thresholds is -0.74V to 5.35V and the program will not
allow the under to be greater than the over voltage
threshold.
These monitor thresholds can be applied globally to
each and every cell in the system or customized for the
cells connected to an individual board by clicking the
desired option button. Individual boards are selected
for programming by the left hand tabs in multiple
board systems.
14B
4: READ CELL VOLTAGES
The essential function of the LTC6803-1 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 VOLTAGE
button. This com-
mands an A/D conversion of all 12-cell voltages in the
time configured from the selected Set CDC option in
the
SET I/O MODE
box. The actual cell voltage mea-
surements are not displayed until the
READ CELL
VOLTAGE
command button is clicked.
15B
5: 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 important feedback for battery charg-
ing algorithms to know when to start or stop charging.
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
FLAG
REGISTERS
section of the control panel.
One of the configuration options is to mask these flags
from appearing in the register bytes that are read from
the LTC6803-1. This feature can be used to prevent or
allow these flags to affect a control algorithm. A check
box is provided for each cell in a stack to select the
mask interrupt option for that cell. To implement the
masking requires checking the box and then writing
the new configuration with a
WRITE CONFIG
button
push.
If the measured voltage of a cell is within the monitor-
ing thresholds all indications for the cell appear green.
DC1651A
7
16B
5: READ TEMPERATURE
The LTC6803-1 has three ADC channels dedicated to
measuring temperature. The temperature indications
are for the internal die temperature of the LTC6803-1
and two externally connected thermistors. The display
returns a voltage measurement.
The internal die temperature sensor produces a voltage
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 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
:
will produce a half scale voltage reading at 25°C.
Any thermistor value may be used but scaling the vol-
tage measurement may require changing the values of
resistors R29 and R30 on the DC1651A circuit board.
To take a temperature reading simple click the
START
TEMP
command button to make the LTC6803-1 ADC
conversion followed by clicking the
READ TEMP
command button to download the data from the board
and display the voltage readings.
17B
6: READ AN INDIVIDUAL CELL OR TEMPERATURE
18B
Each cell and each temperature channel has a check
box to allow individual measurements. Checking
these “Only” boxes sends the command (
STARTCELL
VOLT
then
READCELL VOLT
,
START TEMP
then
READ
TEMP
) to read only that channel and display its
status. Cell 8 and Internal Temp are shown in the
example screen above. Older or stale readings for all
other cells and temperatures are faded out.
DC1651A
8
19B
8: DISCHARGE CELLS
Another major feature of the LTC6803-1 is the ability to
remove charge from individual cells. This can help to
distribute the cell charge evenly over a stack of batte-
ries. DC1331C contains a P channel Mosfet in series
with a 33
:
resistor across each cell connection. When
enabled, a cell is loaded and charge is pulled from the
cell with energy dissipated in the switch and resistor.
A check box is provided for each cell to be discharged.
Checking this box (Cell 3 in the above example screen
shot) and then writing the new configuration with a
WRITE CONFIG
button push will load the cell.
IMPORTANT NOTE:
The discharge transistors are au-
tomatically turned off momentarily while the A/D con-
verter is measuring the cell voltage using the normal
STARTCELL VOLT
command. This prevents any vol-
tage drop errors caused by the discharge current flow-
ing through the cell inter-connection wiring. An accu-
rate indication of the true state of charge of the cells is
then obtained.
The LTC6803-1 offers the option of keeping the dis-
charge transistors on while measuring the cell voltag-
es. This is done using the
STARTCELL hold DCC
command button. A blue indicator is illuminated when
this command has been executed. This lower voltage
reading also includes I*R errors introduced by cabling
and connectors.
20B
OTHER CONTROL FEATURES
Three additional command buttons are provided on the
control screen. The
POLL ADC
and
POLL INTERRUPT
command buttons are used to test if the ADC is busy
making conversion and to test if any of the LTC6803-1
devices in a system have an interrupt condition respec-
tively. The result of these commands can be observed
by monitoring the serial data output line of the SPI in-
terface to the Bottom Port, J2. There is no indication
provided on the control screen.
The
START OPENWIRE
command button connects the
built in open wire detection circuitry to all cells. This
command must be followed by
READCELL VOLT
command button click to see the result. An open wire
connection to any cell will be indicated by an abnor-
mally high voltage measurement for the cell above the
open wire and a near 0V measurement for the cell with
the open wire.
21B
CONTINUOUS OPERATION
For convenience, the control panel allows for conti-
nuous operation of the DC1651A board. The command
button labeled
START
CONTINUOUS READ CELLS
can
be clicked and the board control is placed in a conti-
nuous loop executing the following commands auto-
matically in the following sequence:
Start cell voltage
Read cell voltage
Start temp
Read temp
Read flags
All values are updated continually (~800ms update
rate). While running, the configuration can be changed
on the fly. Simply changing a configuration item (Dis-
charge cells for example) and clicking the
WRITE
CONFIG
button will implement the new configuration
and return to continuous operation.
A green box in the lower right hand corner indicates
that the system is running continuously. A red box
means that the system is stopped and waiting for a
new command to be sent.
DC1651A
9
22B
DISPLAYING VALID DATA TRANSFERS ONLY
Each time data is transferred from the LTC6803-1 by
the four READ commands (Cell Voltage, Configuration,
Flag Status and Temperature), a Packet Error Code,
PEC, is appended based on the data stream sent. The
control program also calculates a PEC value based on
the data it receives. If the calculated PEC matches the
transmitted value the data transfer is assumed to be
error free and therefore the data is valid.
If the two PEC values do not match, the transmitted
data stream has been somehow corrupted. This type of
data error becomes more of a concern when boards
are stacked and the transmit data stream is leng-
thened. The transmitted and calculated PEC values are
displayed on the GUI and turn red when a mismatch
occurs.
23B
LOW CURRENT STANDBY
An important system consideration is the ability to put
the monitoring circuitry into a low current drain condi-
tion. This is done by setting the LTC6803-1 into its
standby configuration. A command button in the lower
right corner of the screen is provided to facilitate this
function. Once pushed all data and configuration set-
tings are reset and the screen goes white on all indica-
tors.
24B
SELF TEST & DIAGNOSTIC FUNCTIONS
The LTC6803-1 has built in self test and diagnostic
functions. These commands apply a test signal to the
ADC to check that the internal cell voltage and tem-
perature connections are functioning. The cell voltage
and open wire test signals can be applied with or with-
out the discharge transistors active. Checking the func-
tionality of each bit in the internal data registers for cell
voltages and temperatures can also be seen by choos-
ing which test code (0x555 or 0xAAA) to expect to be
returned from the device when a self test command is
issued.
25B
OTHER CONFIGURATION OPTIONS
The SET I/O MODE group of checkboxes can be used
to adjust other features of the LTC6803-1. Configuring
the general purpose I/O pins and setting the type of
activity polling scheme can be selected then configured
with a WRITE CONFIG button push.
DC1651A
10
26B
STACKING BOARDS TO ADD MORE BATTERY CELLS
A unique characteristic of the LTC6803-1 is the ability
to communicate serial data up and down a stack of
devices connected to any number of battery cell
stacks. Likewise any number of DC1651A boards,
monitoring up to 12 cells each, can be stacked in daisy
chain fashion. The control GUI however is limited to
only 10 boards (120 cells maximum). To stack and
control more than one board requires the following
hardware and software modifications:
27B
HARDWARE ADJUSTMENTS
1.
The bottom board on the stack, which connects to
a system controller or to a DC590 Quick Eval link
to a PC, must have its Bottom Port set to voltage
mode. Jumper J8 (VMOD) must be connected to
the ACTIVE position.
A 5K
:
pull-up resistor must
be connected from the SDO output line (connec-
tor J2, pin 5) to the 3V/5V logic power rail of the
circuit driving the bottom SPI port.
2.
Every board connected above the bottom board
must have its serial ports set to Current Mode.
Connect Jumper J8 to the GND position on each
board to set this.
3.
The final board on the top of the stack must have
J4 (TOS) set to ACTIVE. Connect J4 (TOS) on all
other boards to the GND position.
4.
A ribbon cable must connect the Top Port (J3) of a
lower board to the Bottom Port (J2) of the next
board up on the stack. The daisy chain linking
with ribbon cables from the Top port of a lower
board on the stack to the Bottom port of the next
board above it establishes the serial data link for
the entire stack.
28B
CAUTION! CAUTION! CAUTION!
As battery cells are stacked on top of each other, great
care must be taken to prevent damage and personal
injury from the very high voltage potentials that may be
present. Do not allow short circuit connections, wheth-
er electrical or human, between a high voltage point
and the system or chassis ground at the bottom of the
stack. Be very careful and respect the potential danger
of high voltage!
29B
IMPORTANT NOTE FOR DEMONSTRATION OR
EVALUATION WHEN NOT USING BATTERY CELLS IN
A STACK
When using DC1651A boards in a stacked application
where a resistor string is used to simulate cell voltages
an extra wire must be added to connect the V+ poten-
tial of a lower board to the V- potential of the next
board up on the stack. Connector J1, pin 16 of a the
lower board must be connected to the connector J1,
pin 1 or pin 4 of the next board above it on the stack.
The wire making this connection should be kept as
short as possible (less then 2 inches or 5 cm).
This
supply connection is not provided by the ribbon con-
nector and is required to enable data communication
up and down the stack.
DC1651A
11
30B
SOFTWARE ADJUSTMENTS
The GUI program can control up to ten boards on a
stack.
1.
Select the number of boards on the stack from the
pop up window located near the command buttons
at the bottom of the screen.
2.
Select whether the Operating Configuration (CDC
Comparator) and Over/Under voltage thresholds
for each board are to be the same (GLOBAL) or dif-
ferent for each board (CUSTOM) and set the duty
cycle and voltages accordingly.
3.
A tab will appear on the left edge of the control
panel for each board on the stack. Clicking on any
of these tabs will transfer control commands and
data to and from the display screen to that selected
board.
31B
COLOR CODED STATUS PANEL
The color-coded status panel will expand to include all
boards connected in a stack. Each small square in this
array represents an individual battery in the stack of
boards. The intent of this display is to provide a way to
see the status of all cells at a glance. The significance
of the colors used is explained in the legend on the
screen.
Any grayed box indicates that the cell’s interrupt flag
has been masked so the LTC6803-1 is no longer re-
porting this status. The cell voltage value measured for
this cell however is still accurate.
The next pages are the schematic for DC1651A. Con-
sult the data sheet for detailed information concerning
the operation of the LTC6803-1.
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12
