19-4045; Rev 0; 2/08
MAX16824 Evaluation Kit
General Description
The MAX16824 evaluation kit (EV kit) demonstrates a
high-voltage, 3-channel, linear high-brightness LED
(HB LED) driver using the MAX16824 IC. This EV kit is
configured to supply an LED current of 100mA per
channel and operates from a 0.5A, 6.5V to 28V rated
power supply.
The EV kit eases evaluation of the MAX16824 pulse-
width-modulation (PWM) dimming-control feature by
providing three independent PWM inputs to all three
channels. Each PWM input accepts a digital signal up
to 5kHz.
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
Three Independent PWM Inputs
o
PWM Dimming Control Up to 5kHz
o
Fully Assembled and Tested
Evaluates: MAX16824
Component List
DESIGNATION
QTY
DESCRIPTION
1µF ±10%, 50V X7R ceramic
capacitor (1210)
Murata GRM32RR71H105K or
TDK C3325X7R1H105K
1µF ±10%, 10V X5R ceramic
capacitor (0603)
Murata GRM188R61A105K
2Ω ±1%, 0.25W sense resistors
(1206)
IRC WCR-WCR1206LF-2R00-F
Linear HB LED driver
(16-pin TSSOP-EP*)
Maxim MAX16824AUE+
PCB: MAX16824 Evaluation Kit+
PART
MAX16824EVKIT+
Ordering Information
TYPE
EV Kit
C1
1
+Denotes
lead-free and RoHS-compliant.
Quick Start
Required Equipment
Before beginning, the following equipment is needed:
•
MAX16824 EV Kit
•
6.5V to 28V, 0.5A adjustable DC power supply
•
Logic function generator
•
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
C2
1
R1, R2, R3
3
U1
—
1
1
*EP
= Exposed paddle.
Procedure
Component Suppliers
SUPPLIER
IRC, Inc.
Murata Mfg. Co.,
Ltd
TDK Corp.
PHONE
361-992-7900
770-436-1300
847-803-6100
WEBSITE
www.irctt.com
www.murata.com
www.component.tdk.com
The MAX16824 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.
1) Set the power-supply output to over V
FLED
+ 1.7V.
2) Set the function generator to produce a 5V-logic,
1kHz square wave with a 50% duty cycle.
3) Disable the power-supply and function generator
output.
4) Connect the power-supply ground to the GND pad
next to the IN pad.
5) Connect the power-supply positive output to the IN
pad.
6) Connect the logic function generator ground to the
GND pad next to the PWM pads.
Note:
Indicate that you are using the MAX16824 when contact-
ing these component suppliers.
________________________________________________________________
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.
MAX16824 Evaluation Kit
Evaluates: MAX16824
7) Connect the logic function generator output to each
of the PWM pads (PWM1, PWM2, and PWM3).
8) Connect one LED load anode to each LED output
pad (LED1+, LED2+, or LED3+).
9) Connect each LED load cathode to the correspond-
ing LED input pad (LED1-, LED2-, or LED3-).
10) Enable the power-supply output.
11) Enable the logic function generator signal output.
12) Verify that the attached LEDs are illuminated.
Output Current Setting
The current for each MAX16824 EV kit LED channel
(I
LED1
, I
LED2
, and I
LED3
) is configured to 100mA by
three sense resistors (R1, R2, and R3, respectively).
See the equation below to select a different LED cur-
rent 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 resis-
tor (R1, R2, or R3) or the LED load.
Do not set the LED
current above 150mA.
Use the following equation to
calculate the value of the new resistor:
R_
=
200mV
I
LED _
Detailed Description of Hardware
The MAX16824 EV kit demonstrates a high-voltage,
3-channel, linear high-brightness LED driver using the
MAX16824 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 MAX16824 IC controls the
LED current by maintaining a 200mV drop across each
external sense resistor (R1, R2, and R3). The EV kit
operates from a 0.5A, 6.5V to 28V rated power supply.
The three independent PWM inputs (PWM1, PWM2,
and PWM3) control dimming for each channel. Each
PWM input functions as an active-high enable for the
corresponding LED channel.
The MAX16824 features an exposed paddle that uses
the top-layer and bottom-layer PCB copper as a
heatsink. The exposed paddle connects to GND.
where I
LED_
is the desired LED current and R_ is the
resistor value required to set the desired current of the
LED channel.
High Input Voltage
and Thermal Protection
The MAX16824 IC operates in linear mode. As a result,
the IC can dissipate significant power if operated using a
high input voltage and a small V
FLED
. High-power dissi-
pation may cause the IC to go into thermal shutdown.
Refer to the
Thermal Protection
section in the MAX16824/
MAX16825 IC data sheet for more information.
LED Dimming
The MAX16824 EV kit features three independent PWM
pads used for controlling LED brightness for each
channel. Each channel can have a different dimming
signal pattern. Use a digital PWM signal with a 5V logic
level and a switching frequency between 100Hz and
5kHz. Frequencies lower than 100Hz can introduce
flickering in the light output. Vary the duty cycle of the
signal to adjust the LED brightness. LED brightness
increases as the duty cycle increases and vice versa.
When the PWM signal’s duty cycle is 100%, the LEDs
are continuously on. At 0% duty cycle, the outputs are
disabled.
LED Load Configuration
The MAX16824 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.
2
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