QUICK START GUIDE FOR DEMONSTRATION CIRCUIT DC915
WLED DRIVER & LCD BIAS
1
LT3466EDD-1
DESCRIPTION
Demonstration circuit DC915 features LT3466-1
high efficiency white LED driver and step-up con-
verter. There is one LED driver output for 8
WLEDs and 2 normal outputs for LCD. VO1
drives 8 LEDs in series with 15mA LED current
and VO2/VO3 can delivery +/- 15V at 10mA cur-
rent. If the charge-pump circuitry (C4, C5 and D1),
which generates VO3, is removed, VO2 can de-
liver over 35mA of current. The input voltage
range is 3V to 14V, which can go as low as 2.7V
with slightly reduced output current.
Each output channel has a jumper (JP1 or JP2)
for enabling the output(s) and a CTRL pin (CTRL1
or CTRL2) for LED brightness (current) control or
VO2/VO3 voltage adjustment. Placing the jump-
ers to “/SD” turns off the WLEDs or VO2/VO3, and
jumpers to “EN” enables the selected channel of
the LT3466-1. Modulating the voltage at CTRL1
or CTRL2 pin respectively can change the LED
current at VO1 or VO2/VO3 voltages. As the volt-
age on the CTRL1 pin increases from 0V to 1.6V,
the feedback voltage across the LED current pro-
gramming resistor increases from 0 to 200mV,
varying the LED current from 0 to 15mA. Simi-
larly, VO2/VO3 voltages increase with voltage on
CNTL2. The “CTRL to FB” curves are show in the
datasheet.
JP3 can conveniently set 8 WLEDs (JP3 jumper at
top position), 6 WLEDs (JP3 jumper at bottom po-
sition), or open circuit protection test (no jumper),
while FB1 terminal monitors the WLED current
(VFB1/R1).
The overall solution occupies less than 1.62 cm
2
with components on one side of the PCB.
Design files for this circuit board are available.
Call the LTC factory.
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LT is a trademark of Linear Technology Corporation
Table 1.
Performance Summary (T
A
= 25°C unless otherwise noted)
PARAMETER FOR LED DRIVER CONDITION VALUE
Minimum Input Voltage 3V
Maximum Input Voltage 14V
LED Current With R1=13.3 ohms 15mA
VO2 15V/10mA
VO3 -14.5V/10mA
Typical Overall Efficiency 3.6V input 82%
Typical Switching Frequency With 63.4K
Ω
timing resistor 800kHz
Typical Shutdown Current 3.6V input, both boost shutdown 27uA
Typical OVP at VO1 LED string open 39.5V
