DEMO MANUAL DC2472A
18-CELL STIMULUS BOARD
DESCRIPTION
Demonstration circuit 2472A is a USB-powered resistor-
string, voltage ladder with variable output. The DC2472A
provides a simple battery stack simulator for connection
directly to most of Linear Technology’s LTC68xx “battery
stack monitor” demo boards.
Using the 5V from a USB charger, the DC2472 generates
an isolated high voltage from ~25V to ~75V, applied to
a resistor string generating 18 voltages taps. These taps
provide a simulation of a string of series connected bat-
tery cells, each tap pair providing nominally the same
virtual cell voltage. The input voltage to the resistor string
is adjustable by an on-board potentiometer to furnish a
divided output voltage in a range of about 1.5V-4.2V per
cell to demonstrate operation at conditions comparable
to a wide range of cell chemistries.
CONNECTION TO AN LTC68XX DEMO-BOARD
1. The back side of the DC2472A shows where the
LTC68xx demo board connectors should be attached.
Simply line up the finger contacts with the associated
screw terminal connector according to whether the
connector is a 16- or 19-contact model. The screws
for securing the connections should be facing the com-
ponent side of the DC2472A. Torque the 16- or 19-posi-
tion connections to 0.2-0.25Nm. A 22-contact adapter
(e.g. DC2701A) should be torqued to 0.22-0.25Nm.
See Figure 1 for example installations.
2. In the case of a 15-cell demo (e.g. for LTC6812), the
pinout requires every sixth tap pair to be shorted over.
To accomplish this, place JP19, JP20, and JP21 to the
“15” position. In all other usages, leave those jumpers
in the ‘18’ position. Note that cell voltages will increase
20% with placement of jumpers in the “15” position
due to the reduced division factor.
3. A USB to USB MICRO-B cable (like non-Apple cell
phone charger) provides a simple means of powering
the DC2472A from a 1A USB charger (some computer
ports may not provide adequate current for stable
output levels). Alternatively, a 5V bench power supply
can be connected to the power input turrets (+5V &
+5V COM) with clip-leads. Note that the +5V connec-
tions are isolated with respect to the GND turret of the
DC2472A, so the +5V COM and GND cannot be used
interchangeably.
WARNING – THIS BOARD GENERATES VOLTAGE POTEN-
TIALS UP TO 80V
Design files for this circuit board are available at
http://www.linear.com/demo/DC2472A
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Analog
Devices, Inc. All other trademarks are the property of their respective owners.
Typical 12-Cell Demo
Typical 15- or 18-Cell Demo
Typical DC2701 Adapter Usage
Figure 1. Output Connection Options
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DEMO MANUAL DC2472A
QUICK START PROCEDURE
1. Power up the DC2472A from the USB cable or bench
supply.
2. Once powered, the Blue LED1 should illuminate.
3. Adjust potentiometer to provide a desired equivalent
cell voltage as shown in Figure 2. Note that there will
be some variation in voltages amongst “cells” due to
component tolerances.
4. Operate the LTC68xx demo as applicable. Note that
resistor-string battery simulations (and DC2472A in
particular) cannot generally generate currents suitable
for properly demonstrating cell-balancing activity.
5. Jumpers JP0 through JP18 may be used to discon-
nect particular tap signals for demonstrating ‘open-
wire’ scenarios. Relocating a particular jumper to the
NC position will disconnect a cell path to simulate a
broken connection.
Figure 2. Cell Voltage Setting
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DEMO MANUAL DC2472A
THEORY OF OPERATION
The DC2472A is a resistor-string voltage-divider ladder
powered by a variable voltage. A block diagram is shown
in Figure 3 and shows the key functional elements. The
heart of the circuit is an LT8302 isolated flyback converter
that produces both about 40V and 80V from a 5V source
such as a USB charger. The source 5V does not share
a galvanic connection to the equivalent cell-stack being
simulated so that many units can be operated without any
‘ground-loop’ fault currents. The 40V powers an LT6650
amplifier whose 15V output is scaled by a potentiometer
to create a variable voltage. The variable voltage is ampli-
fied 5x by an LTC6090 op amp that is powered from the
80V. The LTC6090 drives an 18-tap resistor ladder to
generate the equivalent series-connected cell voltages.
Each tap pair includes a significant capacitance to pro-
vide steady voltage in the presence of digitizing activity
ISOLATED
FLYBACK
DC/DC
CONVERTER
80V
AMPLIFIER
A=5
w/C
LOAD
COMP
.
by the demo board that is being powered. The amplifier
is decoupled and stabilized to operate with the capacitive
load but can still quickly respond to larger load demands
(i.e. the supply dynamics of the battery monitoring cir-
cuit being powered). To also support 6-cell and 12-cell
demonstrations, LTC6090 op amps also buffer 1/3 and
2/3 of the main LTC6090 voltage to provide stabilization
at those points in the ladder that might have to supply
current to a monitoring demo. To support a 15-cell demo,
every 6th cell divider can be shorted over with a jumper
(note that 15-cell demo circuits are designed to accept
their cell inputs in a compatible pinout with 3 zero-volt
cells). The lower voltage LTC6090 units include voltage
reduction Zener diodes to minimize heating of the IC die
if driving load current.
5V
25V-75V
TAP18
3 RESISTOR STRING
15V
REFERENCE
15/18 RESISTOR STRING
AMPLIFIER
A=1
w/C
LOAD
COMP
.
TAP12
18 TAPS
VARIABLE
ATTENUATOR
AMPLIFIER
A=1
w/C
LOAD
COMP
.
Figure 3. Block Diagram of the DC2472A
TAP6
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DEMO MANUAL DC2472A
DEMONSTRATION BOARD IMPORTANT NOTICE
Linear Technology Corporation (LTC) provides the enclosed product(s) under the following
AS IS
conditions:
This demonstration board (DEMO BOARD) kit being sold or provided by Linear Technology is intended for use for
ENGINEERING DEVELOPMENT
OR EVALUATION PURPOSES ONLY
and is not provided by LTC for commercial use. As such, the DEMO BOARD herein may not be complete
in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including but not limited to product safety
measures typically found in finished commercial goods. As a prototype, this product does not fall within the scope of the European Union
directive on electromagnetic compatibility and therefore may or may not meet the technical requirements of the directive, or other regulations.
If this evaluation kit does not meet the specifications recited in the DEMO BOARD manual the kit may be returned within 30 days from the date
of delivery for a full refund. THE FOREGOING WARRANTY IS THE EXCLUSIVE WARRANTY MADE BY THE SELLER TO BUYER AND IS IN LIEU
OF ALL OTHER WARRANTIES, EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING ANY WARRANTY OF MERCHANTABILITY OR FITNESS
FOR ANY PARTICULAR PURPOSE. EXCEPT TO THE EXTENT OF THIS INDEMNITY, NEITHER PARTY SHALL BE LIABLE TO THE OTHER FOR
ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES.
The user assumes all responsibility and liability for proper and safe handling of the goods. Further, the user releases LTC from all claims
arising from the handling or use of the goods. Due to the open construction of the product, it is the user’s responsibility to take any and all
appropriate precautions with regard to electrostatic discharge. Also be aware that the products herein may not be regulatory compliant or
agency certified (FCC, UL, CE, etc.).
No License is granted under any patent right or other intellectual property whatsoever.
LTC assumes no liability for applications assistance,
customer product design, software performance, or infringement of patents or any other intellectual property rights of any kind.
LTC currently services a variety of customers for products around the world, and therefore this transaction
is not exclusive.
Please read the DEMO BOARD manual prior to handling the product.
Persons handling this product must have electronics training and
observe good laboratory practice standards.
Common sense is encouraged.
This notice contains important safety information about temperatures and voltages. For further safety concerns, please contact a LTC application
engineer.
Mailing Address:
Linear Technology
1630 McCarthy Blvd.
Milpitas, CA 95035
Copyright © 2004, Linear Technology Corporation
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