19-4052; Rev 0; 2/08
MAX16825 Evaluation Kit
General Description
The MAX16825 evaluation kit (EV kit) demonstrates a
high-voltage, 3-channel, linear high-brightness LED (HB
LED) driver using the MAX16825 IC. This EV kit is config-
ured to supply an LED current of 100mA per channel and
operates from a 0.5A, 6.5V to 28V rated power supply.
The MAX16825 EV kit uses a standard 4-wire SPI™
interface for independently controlling each of the three
LED channels. The MAX16825 EV kit also integrates a
USB-to-SPI interface circuit based on Maxim’s
MAXQ2000 microcontroller. The EV kit includes
Windows 2000/XP/Vista
®
-compatible software that pro-
vides a simple graphical user interface (GUI) for exer-
cising the features of the MAX16825. The EV kit can
also interface with a user-supplied SPI circuit for stand-
alone operation.
Features
o
Operates from a 6.5V to 28V, 0.5A Supply
o
3 Channels for Driving High-Brightness LEDs
o
100mA LED Current per Channel
o
Evaluates a Stand-Alone 4-Wire SPI Interface
o
USB-PC Interface (Cable Included)
o
Windows 2000/XP/Vista (32-Bit)-Compatible
Software
o
Fully Assembled and Tested
Evaluates: MAX16825
Ordering Information
PART
MAX16825EVKIT+
TYPE
EV Kit
+Denotes
lead-free and RoHS-compliant.
Component List
DESIGNATION
C1, C3–C10, C17
QTY
10
DESCRIPTION
0.1µF ±10%, 16V X7R ceramic
capacitors (0603)
TDK C1608X7R1C104K
10µF ±20%, 6.3V X5R ceramic
capacitors (0805)
TDK C2012X5R0J106M
10pF ±5%, 50V C0G ceramic
capacitors (0603)
TDK C1608C0G1H100J
1µF ±10%, 10V X5R ceramic
capacitors (0603)
Murata GRM188R61A105K
22pF ±5%, 50V C0G ceramic
capacitors (0603)
TDK C1608C0G1H220J
3300pF ±10%, 50V X7R ceramic
capacitor (0603)
TDK C1608X7R1H332K
1µF ±10%, 50V X7R ceramic
capacitor (1210)
Murata GRM32ER71H105K or
TDK C3325X7R1H105K
DESIGNATION
D1
FB1
H1, J1
J2
P1
R1
R2
R3
R4
R5
R6, R7
R8, R9, R10
R11
QTY
1
0
0
0
1
1
1
1
1
1
2
3
0
DESCRIPTION
Green LED (0603)
Panasonic LNJ314G8TRA
Not installed, ferrite-bead inductor
(0603)
Not installed, dual-row (2 x 5) 10-
pin headers
Not installed, dual-row (2 x 4) 8-
pin header
USB type-B right-angle female
receptacle
0Ω ±5% resistor (0603)
220Ω ±5% resistor (0603)
10kΩ ±5% resistor (0603)
2.2kΩ ±5% resistor (0603)
1.5kΩ ±5% resistor (0603)
27Ω ±5% resistors (0603)
2Ω ±1%, 0.25W sense resistors
(1206)
IRC WCR-WCR1206LF-2R00-F
Not installed, resistor (0402)
C2, C13, C15
3
C11, C12
2
C14, C16, C22
3
C18, C19
2
C20
1
C21
1
SPI is a trademark of Motorola, Inc.
Windows Vista is a registered trademark of Microsoft Corp.
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim's website at www.maxim-ic.com.
MAX16825 Evaluation Kit
Evaluates: MAX16825
Component List (continued)
DESIGNATION
U1
QTY
1
DESCRIPTION
SPI-controlled linear HB LED
driver (16-pin TSSOP-EP*)
Maxim MAX16825AUE+
Low-power 16-bit microcontroller
(68-pin QFN-EP*, 10mm x 10mm)
Maxim MAXQ2000-RAX+
93C46 type 3-wire EEPROM
(8-pin SO)
UART-to-USB converter
(32-pin TQFP, 7mm x 7mm)
3.3V regulator (5-pin SC70)
Maxim MAX8511EXK33+T
(Top Mark: AEI)
2.5V regulator (5-pin SC70)
Maxim MAX8511EXK25+T
(Top Mark: ADV)
16MHz crystal
6MHz crystal
USB high-speed A-to-B cable, 6ft
PCB: MAX16825 Evaluation Kit+
TROUBLESHOOTING_USB.PDF
FILE
INSTALL.EXE
MAX16825.EXE
FTD2XX.INF
UNINST.INI
SUPPLIER
IRC, Inc.
Murata Mfg. Co.,
Ltd
Panasonic
TDK Corp.
Component Suppliers
PHONE
WEBSITE
361-992-7900 www.irctt.com
770-436-1300 www.murata.com
800-344-2112 www.panasonic.com
847-803-6100 www.component.tdk.com
U2
1
U3
U4
1
1
Note:
Indicate that you are using the MAX16825 when contact-
ing these component suppliers.
MAX16825 EV Kit Files
DESCRIPTION
Installs the EV kit files on
your computer
Application program
USB device driver file
Uninstalls the EV kit
software
USB driver installation help
file
U5
1
U6
Y1
Y2
—
—
1
1
1
1
1
*EP
= Exposed paddle.
Quick Start
Required Equipment
Before beginning, the following equipment is needed:
• MAX16825 EV kit (USB cable included)
• 6.5V to 28V, 0.5A adjustable DC power supply
• User-supplied Windows 2000/XP/Vista PC with a
spare USB port
• Three LED loads, each rated as follows:
Current rating
≥
100mA
Total LED string forward voltage V
FLED
≤
26.3V
• See the
LED Load Configuration
section for more
information
Note:
In the following sections, software-related items
are identified by bolding. Text in
bold
refers to items
directly from the EV kit software. Text in
bold and
underlined
refers to items from the Windows operat-
ing system.
Procedure
The MAX16825 EV kit is fully assembled and tested.
Follow the steps below to verify board operation.
Caution: Do not turn on the power supply until all
connections are completed.
2
1) Visit www.maxim-ic.com/evkitsoftware to download
the latest version of the EV kit software,
16825Rxx.ZIP. Save the EV kit software to a tempo-
rary folder and uncompress the ZIP file.
2) Install the EV kit software on your computer by run-
ning the INSTALL.EXE program inside the tempo-
rary folder. The program files are copied and icons
are created in the Windows
Start | Programs
menu. All EV kit files are automatically installed.
3) Set the power-supply output to over V
FLED
+ 1.7V.
4) Disable the power-supply output.
5) Connect the power-supply ground to the GND pad
next to the VIN pad.
6) Connect the power-supply positive output to the
VIN pad.
7) Connect one LED load anode to each LED output
pad (LED1+, LED2+, or LED3+).
8) Connect each LED load cathode to the correspond-
ing LED input pad (LED1-, LED2-, or LED3-).
9) Connect the USB cable from the PC to the EV kit
board. A
New Hardware Found
window pops up
when installing the USB driver for the first time. If
you do not see a window that is similar to the one
_______________________________________________________________________________________
MAX16825 Evaluation Kit
described above after 30s, remove the USB cable
from the board and reconnect it. Administrator priv-
ileges are required to install the USB device driver
on Windows.
10) Follow the directions of the
Add New Hardware
Wizard
to install the USB device driver. Choose the
Search for the best driver for your device
option.
Specify the location of the device driver to be
C:\Program Files\MAX16825
(default installation
directory) using the
Browse
button. During device dri-
ver installation, Windows may show a warning mes-
sage indicating that the device driver Maxim uses does
not contain a digital signature. This is not an error con-
dition and it is safe to proceed with installation. Refer to
the TROUBLESHOOTING_USB.PDF document
included with the software for additional information.
11) Enable the power-supply output.
12) Start the EV kit software by opening its icon in the
Start | Programs
menu. The MAX16825 EV kit soft-
ware main window appears, as shown in Figure 1.
13) Select the
Output Enable
checkbox and any of the
Channel_
checkboxes.
14) Verify that the corresponding attached LEDs are
illuminated.
The software features a demo mode that is available by
selecting the
View | Demo Mode
menu item. When
operating in demo mode, all software communication to
the EV kit hardware is disabled and most of the soft-
ware’s GUI is functional. This feature enables the user
to evaluate the software without hardware connectivity.
The left-bottom status bar provides the USB-to-SPI
communication status. The right-bottom status bar pro-
vides the current program status. The MAX16825 EV kit
software configures the on-board SPI communication to
8kHz by default.
Evaluates: MAX16825
Software Startup
Upon starting the program, select the
Output Enable
checkbox to enable the LED outputs. Deselecting the
Output Enable
checkbox disables all three LED out-
puts. The
Channel_
checkboxes enable and disable
individual channels.
General-Purpose 3-Wire (SPI) Interface Utility
The general-purpose
3-wire interface
utility (Figure 2)
can also be used to communicate with the MAX16825
using low-level SPI commands. Select the
Options |
Interface
menu item and select the
3-wire interface
tab
to access the utility. The utility configures the 3-wire ser-
ial-interface parameters, such as MSB position, CPOL,
CPHA, MOSI/MISO inverted logic, CS active state (high
or low), SPI clock (SCLK) speed, and custom selection
of SPI signal pins. The data to be sent is 8-bit data rep-
resented by a two-digit hexadecimal code. The code is
entered in the
Data bytes to be written
edit box and
transmitted by clicking on the
Send Now
button.
General Troubleshooting
Problem: Software reports it cannot find the inter-
face circuit.
• Is power LED D1 lit?
• Is the USB cable connected to the PC and EV kit?
• Is power applied to the VIN PCB pad?
• Has Windows plug-and-play detected the board?
Bring up the
Control Panel > System > Device
Manager,
and look at what device nodes are indi-
cated for USB. If there is an unknown device node
attached to the USB, delete it. This process forces
plug-and-play to try again.
Figure 1. MAX16825 Evaluation Kit Software—Graphical User
Interface (GUI)
Detailed Description of Software
Graphical User Interface
The main window’s GUI (Figure 1) is simple to use. A
mouse or the keyboard’s tab key is used to navigate
through the controls. The correct SPI write operation is
generated to update the internal registers of the
MAX16825 when any of these controls are used.
_______________________________________________________________________________________
3
MAX16825 Evaluation Kit
Evaluates: MAX16825
Figure 2. The 3-Wire Interface Window Provides Direct, Low-Level Access to the MAX16825 and 3-Wire Serial Interface
4
_______________________________________________________________________________________
MAX16825 Evaluation Kit
Detailed Description of Hardware
The MAX16825 EV kit demonstrates a high-voltage, 3-
channel, linear high-brightness LED driver using the
MAX16825 IC in a 16-pin TSSOP surface-mount pack-
age. This EV kit is configured to supply an LED current
of 100mA per channel. The MAX16825 IC controls the
LED current by maintaining a 200mV drop across each
external sense resistor (R8, R9, and R10). The EV kit
operates from a 0.5A, 6.5V to 28V rated power supply.
The MAX16825 EV kit uses a standard 4-wire SPI inter-
face for independently controlling each of the three
individual channels. Only the components in the Figure
3 schematic are required when using a user-supplied
SPI interface. The MAX16825 integrates a USB-to-SPI
interface circuit that is based on Maxim’s MAXQ2000
16-bit microcontroller. The EV kit includes Windows
2000/XP/Vista-compatible software that provides a GUI
for exercising the MAX16825 features. The components
on the Figure 4 schematic are only required for PC
evaluation and are not needed for an HB LED design.
The MAX16825 features an exposed paddle that uses
the top-layer and bottom-layer PCB copper as a
heatsink. The exposed paddle connects to GND.
LED Load Configuration
The MAX16825 EV kit can drive three separate LED
loads. Each LED load can consist of multiple LEDs con-
nected in series. The LED load’s forward voltage can
be up to 26.3V. The EV kit drives LEDs rated for at least
100mA. Proper heat sinking of the LEDs is important for
optimum LED performance and durability.
Evaluates: MAX16825
Output Current Setting
The current for each MAX16825 EV kit LED channel
(I
LED1
, I
LED2
, and I
LED3
) is configured to 100mA by
three sense resistors (R8, R9, and R10, respectively).
See the equation below to select a different LED current
and a new resistor value. If designing for a higher LED
current, verify that the desired current setting does not
exceed the power rating of the corresponding resistor
(R8, R9, R10) or the LED load.
Do not set the LED cur-
rent above 150mA.
Use the following equation to cal-
culate the value of the new resistor:
R_
=
200mV
I
LED _
where I
LED_
is the desired LED current and R_ is the
resistor value required to set the desired current of the
LED channel.
_______________________________________________________________________________________
5
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