DC1019A - Demo Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1019A
DUAL WHITE LED DRIVER CONVERTER
LT3497EDDB
DESCRIPTION
WARNING!
Do not look directly at operating LED.
This circuit produces light that can damage eyes.
Demonstration circuit 1019A is a Dual White LED
Driver Converter featuring the LT®3497 in a 3mm x
2mm DFN package. The demo circuit demonstrates
small size and low component count in two independent Boost Circuits. It drives two independent
LED strings at 20mA from a 3V-10V input. Other features of the LT3497, such as the internal schottky diodes, the high switching frequency and the internal
open circuit protection, allow the use of tiny components. Different dimming controls can be implemented on the demo board. Optional N-MOSFET
placeholders are provided to test direct PWM dim-
ming. Analog dimming is done via the
SHDN/DIMMING CONTROL terminals. Please refer to
the quick start procedure. The high side current sensing feature of the LT3497 allows “one wire” current
source, i.e. the low side of the LED string can return
to ground anywhere.
The LT3497 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 1019A.
Design files for this circuit board are available. Call
the LTC factory.
LTC, LT is a registered trademark of Linear Technology Corporation
Table 1. Performance Summary (TA = 25°C)
SYMBOL
PARAMETER
CONDITIONS
MIN
VIN
Input Supply Range **
3
IOUT
Output Current
19
VOUT
Output Voltage
η
Efficiency
VIN=3.6V
VOPEN
CAP pin Over voltage Protection
LED Open
IQ
Quiescent Current
IQSHDN
Quiescent Current in Shutdown
Fs
Switching Frequency
30
TYP
20
MAX
UNITS
10
V
21
mA
19.5
V
72.3
%
34
V
VIN = 4.2V, CTRL=ON, LEDs open
15
mA
VIN = 4.2V, CTRL=OFF
10
µA
2.8
MHz
1.8
32
2.3
** The Input Supply Range of the Demo Circuit 1019A is limited by Maximum Input Voltage of the LT3497.
Always ensure that this level is not exceeded.
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1019A
DUAL WHITE LED DRIVER CONVERTER
QUICK START PROCEDURE
Demonstration circuit 1019A is easy to set up to
evaluate the performance of the LT3497. Refer to Figure 1 for proper measurement equipment setup and
follow the procedure below:
Note: when measuring the input or output voltage
ripple, care must be taken to avoid a long ground lead
on the oscilloscope probe. Measure the input or
output voltage ripple by touching the probe tip
directly across the Vin or Vout and GND terminals.
See Figure 2 for proper scope probe technique.
1. Place jumpers in the following positions to test the
circuit:
JP1
ON
JP2
ON
2. With power off, connect the input power supply to
VIN and GND.
3. Turn on the power at the input.
Note: Make sure that the input voltage does not
exceed 10V.
4. Check for the proper voltages and currents.
Note: If the LEDs do not light up, check the jumper
settings.
5. Once the proper operations are established, adjust
the input within the operating range and observe
the parameters of interest.
6. To test the filtered PWM dimming or the direct DC
dimming, remove the jumper JP1 or JP2, apply the
PWM or the DC signal to the SHDN/DIMMING
CTRL1 or SHDN/DIMMING CTRL2 and observe the
brightness of the LED output.
7. To test the direct PWM dimming, follow the Direct
PWM Dimming section in the datasheet.
Figure 1. Proper Measurement Equipment Setup
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1019A
DUAL WHITE LED DRIVER CONVERTER
Figure 2. Measuring Input or Output Ripple
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1019A
DUAL WHITE LED DRIVER CONVERTER
4
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