QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 590
USB SERIAL CONTROLLER FOR LINEAR TECHNOLOGY QUICKEVAL™ DEMO BOARDS
DESCRIPTION
Demonstration circuit 590 is a USB-based digital con-
troller with generic Serial Peripheral Interface (SPI) and
Inter Integrated Circuit (I
2
C™) ports. It is designed to
mate with Linear Technology’s family of QuickEval™
demonstration boards. The demo board is fully isolated
from the host PC’s ground, and in many cases no exter-
nal power source is required. The evaluation software
automatically detects which demo board is connected
and loads the appropriate control screen.
This system facilitates quick performance evaluation of a
variety of products, including ADCs, DACs, SMBus
power control products, and others.
Figure 1 shows a block diagram of DC590. Power and
digital signal connections are made via a 14-conductor
ribbon cable. In many cases the controller can provide
power for the demonstration circuit as well as digital
signals. The demonstration circuit connections are fully
isolated from the host PC’s ground (earth ground.) Four
of the fourteen ribbon-cable conductors are referred to
earth ground. Thus the isolation barrier is not designed
to withstand large potential differences.
QuickEval is a trademark of Linear Technology Corporation; I C is a trademark of
Philips Electronics N.V.; Adobe is a trademark of Adobe Systems, Inc.
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DATA ISOLATION
(AGILENT HCPL-2300)
4
DATA
I/O
USB
PORT
AUXILIARY
BOARD ID LINES
USB TO
I2C/SPI
CONTROLLER
v
+
14-PIN CONNECTOR
POWER
MANAGEMENT
EXTERNAL
POWER
SWITCHER
SHUTDOWN
(JP1)
LT1761
v
cc
5V
GND
Figure 1. Block Diagram of Demonstration Circuit 590
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 590
USB SERIAL CONTROLLER FOR LINEAR TECHNOLOGY QUICKEVAL™ DEMO BOARDS
Figure 2. Basic Connection
QUICK START PROCEDURE
For proper equipment setup, follow the procedure be-
low:
1.
Do not plug in DC590 before running the installation
NOTE:
The QuickEval demo software requires a PC that
is running Windows 98 (or later), and has an available
USB port.
4.
Connect the demonstration circuit to be evaluated to
program.
2.
Download the QuickEval installation program from
http://www.linear.com/software/.
3.
Run the QuickEval installation program and follow the
DC590 using the supplied 14-conductor ribbon cable.
The demo software detects the circuit and starts the
appropriate control screen.
Each demonstration board also comes with a Quick Start
guide similar to this one. For usage details relevant to a
particular circuit refer to its Quick Start Guide.
on-screen instructions.
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 590
USB SERIAL CONTROLLER FOR LINEAR TECHNOLOGY QUICKEVAL™ DEMO BOARDS
USEFUL SOFTWARE TOOLS
The QuickEval Demo software includes tools for auto-
matic software updates and for quickly retrieving rele-
vant documentation from the World Wide Web.
The Download Datasheets feature is particularly useful
to laptop users, who can use this feature to download
the data sheets and Quick Start guides in one step, thus
making them available even when the laptop is not con-
nected to the internet.
NOTE:
Adobe Acrobat reader is required to view the
To update the software (requires internet connection):
Choose Update from the Tools menu.
This automatically updates the main program and
drivers for individual demo circuits.
To view the Quick Start Guide:
Choose Quick Start Guide from the Tools menu.
To retrieve data sheets (requires internet connection):
Choose Download Datasheets from the Tools menu.
All datasheets and Quick Start guides for all products
in the QuickEval family are downloaded to the
QuickEval program folder and placed in the dsheets
folder.
documents and is available at
http://www.adobe.com.
To use the tools:
Quit the demonstration circuit software or disconnect
the USB cable.
The main control panel appears.
OPTIONAL CONNECTIONS TO THE DC590
In most cases DC590 and the demonstration circuit un-
der evaluation can operate from available USB power,
and thus require nothing more than a USB connection to
the host PC and a ribbon connecting DC590 to the demo
circuit under evaluation. Figure 2 shows this basic
connection.
DC590 offers several other power options, described
below.
Isolated supply options
An external power supply is recommended to reduce the
load on the host computer’s USB port, especially in the
event of faults or short circuits.
An LT1425 switching power supply provides isolated
power to the demonstration circuit under evaluation and
to the isolation circuitry.
The LT1425 switching power supply is enabled by de-
fault but may be disabled by moving jumper JP1 (ISOL
PWR) to the OFF position. This allows the isolated side
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 590
USB SERIAL CONTROLLER FOR LINEAR TECHNOLOGY QUICKEVAL™ DEMO BOARDS
of the board and the demonstration circuit under evalua-
tion to be powered separately. This is recommended
when testing precision components such as high resolu-
tion ADCs and DACs.
Figure 3 shows how to connect an external supply to the
isolated side of the controller and the board under
evaluation.
After disabling the switching supply,
apply
7V–9V between the GND and V+ posts. These posts are
the in, out, and ground terminals of an LT1761 LDO
regulator. The demonstration circuit under evaluation
may draw up to 100mA from V
CC
.
7V
REGULATED
SUPPLY
DEMONSTRATION
CIRCUIT
UNDER
EVALUATION
14-CONDUCTOR
RIBBON
CABLE
USB CABLE
TO HOST PC
Figure 3. Connecting an external supply to the isolated side of the controller
Another option is to supply power to the isolated side of
the controller (see Figure 4) back through the board un-
der evaluation. The LT1761 regulator is reverse-current
protected. This allows any convenient 5V ±10% regu-
lated supply to be used. In this case, the isolation cir-
cuitry on DC590 is also powered from this source.
worst-case current draw by DC590 is 50mA.
5V
REGULATED
SUPPLY
DEMONSTRATION
CIRCUIT
UNDER
EVALUATION
14-CONDUCTOR
RIBBON
CABLE
USB CABLE
TO HOST PC
Figure 4. Supplying power to the controller through the board under evaluation
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 590
USB SERIAL CONTROLLER FOR LINEAR TECHNOLOGY QUICKEVAL™ DEMO BOARDS
LED INDICATORS
Two LED indicators are provided. The “ISOL PWR” LED
is lit when either the onboard switching power supply is
running or external power is applied to the isolated side
of the board.
The “COMMAND” LED indicates that a command has
been sent to the board by the host PC and is waiting to
be executed. The LED may not appear to be blinking in
some cases, as the duty cycle may be very short.
CIRCUIT DETAILS
Schematics for the isolated power supply and optical
signal isolation are attached to the end of this Quick
Start Guide. Example microcontroller code is device-
specific, and may be included in the Quick Start Guide
for the demonstration circuit under evaluation.
OPTICAL ISOLATION
The optical isolation scheme based on the Agilent HCPL
2300 high speed opto isolator and is designed to allow
bidirectional SPI and I
2
C communications. Isolation
schemes that are designed for only SPI or I
2
C will differ
slightly. Contact Linear Technology Applications Engi-
neering for more information.
SWITCHING POWER SUPPLY
The onboard switching supply is based on the LT1425
flyback regulator. Feedback is taken from the primary
side of T1, eliminating the need for optical feedback. T2
and C9 provide common mode filtering. Refer to the
LT1425 data sheet for details of operation.
TROUBLESHOOTING GUIDE
Problem:
DC590 is plugged in, but QuickEval screen
still says “USB Serial Controller Not Connected”
Solution:
The most likely cause is improper installa-
tion of the USB drivers, which causes Windows to rec-
ognize DC590 as an “Unknown Device.” Open the Win-
dows Control Panel, open “System” and click the “De-
vice manager” tab. Open the “Other Devices” item and
look for USB SERIAL CONTROLLER. Select this item and
click the remove button. Unplug DC590, Re-install the
QuickEval software, and follow the on-screen instruc-
tions.
Problem:
Demo board software loads properly, but will
not run or gives “Device Not accessible” errors.
Solution:
Verify that the demo board is properly
powered up. This Quick Start Guide lists the basic power
connections to DC590. Some demo boards may have
additional requirements; refer to the demo board’s Quick
Start guide for details.
Problem:
After connecting the demo board to DC590
with the supplied 14 pin ribbon cable, QuickEval soft-
ware still displays “Evaluation Board is not Connected.”
Solution:
Contact Linear Technology Applications
Engineering.
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