The LM3410 IC is a constant current LED driver useful in either boost
con-verter or SEPIC design applications. A SEPIC (Single Ended Primary
Induct-ance Conver ter) design allows the power supply’s output voltage
to be set above, below or equal to its input voltage. In this
application the chip is configured as a boost-converter (i.e. the output
voltage is greater than the input voltage).
LM3410 LED Driver Circuit Diagram
.
The
LM3410 is available in two fixed-frequency variants. Using either the
525 kHz or 1.6 MHz clock version it is possi-ble to build a ver y
compact LED driver. The output stage can supply up to 2.8 A, allowing
several high-power LEDs to be driven from a rechargeable Lithium cell or
several 1.5 V bat-teries. The chip also features a dimmer input giving
simple PWM brightness control.Output current is defined by an external
shunt resistor. To keep losses low the LM3410 uses an internal voltage
reference of just 190 mV.
Power dissipation in the shunt
resistor is therefore low. Using the desired value of LED current the
value and power dissipation of the shunt resistor is given by:
R_Shunt = 0.19 V/I_LED
P_Shunt = 0.19 V*I_LED
A
10 µH coil (L1) will be suf ficient for most applications providing it
has a suitable satu-ration current rating. The Input and output
capacitors should be 10 µF ceramic t ypes with a low value of E SR .
Many distributor s including Farnell stock these component s. The Diode
should beaSchottky type (as in all switching regulators). The author has
developed a PCB for this design; the corresponding Eagle files can be
freely downloaded from www.elektor.com/090850. In sum-mar y the most
important features of the LM3410 are:
- Integrated 2.8 A MOSFET driver.
- Input voltage range from 2.7 V to 5.5 V.
- Capability to drive up to six series connected LEDs (maximum output 24 V).
- Up to 88 % efficiency.
- Available is 525 kHz and 1.6 MHz versions.
- Allows both boost and SEPIC designs.
- Available in 5 pin SOT23 or 6 pin LLP outline.
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