DC1542A - Demo Manual

DEMO CIRCUIT 1542
QUICK STARTLT3596
GUIDE
LT3596
60V Step-Down 3-Channel LED Driver
DESCRIPTION
Demonstration circuit 1542 is a 60V Step-Down 3Channel LED Driver featuring the LT3596. The demo
board is optimized for 8 LEDs, 100mA output per channel from a 48V input. When different number of LEDs is
used for evaluation, it is recommended to change the
resistor divider (R1 and R4) values according to the
datasheet. The connections between the board and LEDs
strings should be as short as feasible.
pins up to VREF. The switching frequency is set to 1MHz
on the demo circuit for best solution size. The LT3596
internal compensation makes it a lot easier for a designer
to design different application circuits.
The circuit achieves 10,000:1 PWM dimming at 100Hz
PWM frequency. LED dimming can also be done by analog control of the CTRL1-3 pin. If dimming is not required, leave the PWM1-3 and CTRL1-3 terminals unconnected. The demo circuit pulls PWM1-3 and CTRL1-3
Design files for this circuit board are available. Call
the LTC factory.
The LT3596 datasheet gives a complete description of
the part, operation and application information. The datasheet must be read in conjunction with this quick start
guide for demo circuit 1542A.
LTM, LTC and LT are registered trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners.
PERFORMANCE SUMMARY Specifications are at TA = 25°C
SYMBOL
VIN*
VOUT
VOUT(MAX)
IOUT
DIM
FSW
EFE
PARAMETER
Input Supply
Output Voltage
Maximum Output Voltage
Output Current
PWM Dimming Ratio
Switching Frequency
Efficiency
CONDITIONS
MIN
6
8 White LEDs
98
PWM Dimming Frquency = 100Hz
R3=100k
VIN=48V, VOUT=29V, IOUT=100mA, BIAS=5V, No
Dimming
0.9
TYP
29
38
100
10,000:1
1
90
MAX
55
32
102
1.1
UNITS
V
V
V
mA
V
MHz
%
*: Actual VIN range should be determined by the load. For 8 white LEDs per channel, use a 48V input for evaluation.
QUICK START PROCEDURE
Demonstration circuit 1542A is easy to set up to evaluate
the performance of the LT3596. Refer to Figure 1 for
proper measurement equipment setup and follow the
procedure below:
1. With power off, connect the input power supply to
VIN and GND.
2. With power off, connect a 5V bias supply to BIAS
and GND. Bias voltage should be less then 25V.
3. With power off, connect 3 LED strings between
VOUT and LED1-, LED2-, LED3- respectively.
4. Turn on the power at the input. Be careful not to look
at the LEDs directly.
1
LT3596
5. Carefully evaluate all design parameters as needed.
6. To evaluate PWM dimming, apply a PWM signal to
PWM1, PWM2 and/or PWM3. To evaluate 10,000:1
PWM dimming, the PWM signal should have a frequency of 100Hz and the minimum pulse width can
be as low as 1us.
7. To modify the demo board for other applications,
please contact Linear Applications Group for help.
Figure 1. Proper Measurement Equipment Setup
2
LT3596
3
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