DEMO CIRCUIT 1224
QUICK START LT3593
GUIDE
LT3593
LED Driver with One Wire Control and
Output Disconnect
WARNING!
DO NOT LOOK AT OPERATING LED.
This circuit produces light that can damage eyes.
DESCRIPTION
Demonstration circuit 1224 is a LED Driver with
One Wire Control and Output Disconnect featuring
the LT3593. The LT3593 is a step-up current mode
DC/DC converter designed to drive up to 10 white
LEDs in series from a Li-Ion cell. The demo board
has two sections. The top section showcases the
small size LED drive. The maximum current is
20mA. The bottom section is the control section
that generates pulses for the CTRL pin of the LED
driver. The number of pulses and its timing deter-
mine the current and brightness of the LEDs.
The LCD display in the bottom section shows the
status of the commanding LED current level in the
format as “LEVEL=value” and LED current level as
“ILED=value”. The LEVEL value responses to the
UP button SW1 and DOWN button SW2 immedi-
ately. The ILED value only changes to the com-
manding LEVEL value after the SEND/STORE
button SW3 is pushed. Pushing SEND/STORE
button also save the LEVEL value in the memory
of the micro-controller U2 as the default LED cur-
rent level.
The LT3593 datasheet gives complete description
of the part, operation and application information.
The datasheet must be read in conjunction with
this quick start guide for working on or modifying
the demo circuit 1224.
Design files for this circuit board are available.
Call the LTC factory.
, LTC and LT are registered trademarks of Linear Technology Corporation.
ThinSOT and PowerPath are trademarks of Linear Technology Corporation.
PERFORMANCE SUMMARY
Specifications are at T
A
= 25°C
SYMBOL
V
IN
+5V
I
LED_MAX
V
OUT_MAX
η
V
OPEN
Fs
PARAMETER
Input Supply Range
Input Supply for Control Section
Maximum Output LED Current
Maximum Output Voltage
Efficiency
Over voltage Protection
Switching Frequency
CONDITIONS
MIN
3
4.5
19
TYP
5
20
81
79
38
1
MAX
5
5.5
21
40
UNITS
V
V
mA
V
%
V
MHz
V
IN
=5V, 8 White LEDs
V
IN
=3.6V, 8 White LEDs
LED Open
36
0.85
40
1.15
1
LT3593
QUICK START PROCEDURE
Demonstration circuit 1224 is easy to set up to
evaluate the performance of the LT3593. Refer to
Figure 1 for proper measurement equipment setup
and follow the procedure below:
1.
Place
5.
Turn
on the power at the input.
on the power at +5V.
for the proper voltages and currents.
NOTE.
Make sure that the input voltage does not exceed 5V.
6.
Turn
jumpers in the following positions:
7.
Check
PIC
JP1
2.
With power off, connect a 3V to 5V power sup-
ply to V
IN
and GND.
3.
With
NOTE.
By default of the demo board, the current is 20mA when
power is applied the very first time.
8.
Adjust
power off, connect 4.5V to 5.5V power
supply to +5V and GND.
a string of up to 10 LEDs between
LED+ and LED-. The Cathode of the last LED
connects to the LED-.
4.
Connect
the UP (SW1), DOWN (SW2),
SEND/STORE (SW3) to the value of interest be-
tween 0 and 32, where ILED=32 gives 20mA,
ILED=1 gives 625uA, and ILED=0 shuts down
the part.
Figure 1. Proper Measurement Equipment Setup
2
FPGA/CPLD
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