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I am testing below LED Driver Circuitry on breadboard using LM3410X.

LED Driver Input Specs:

Vin & DMM = 5V,

L = 20 uH

R=2 Ohm

Only thing is I have'nt connected LED ( I am testing with 10k resistor as dummy load) But somehow I am getting 4.86 V at o/p ( across 10K load resistor )

Can anybody help me to figure out. Do I need to connect LED string?

Thanks in advance. :)

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So you have set a current of 95mA using R1 = 2\$\Omega\$ (190mV typical reference) and are thusexpecting a voltage of 950V (95mA * 10K) at the output.. this will can damage the chip.

Put some LEDs on there (more than 5V drop!- three or more white/blue LEDs) and see if it still works. You may have fried the chip. See the zener OVP circuit suggestion from the datasheet:

enter image description here

1MHz+ (this one is 1.6MHz) switching supplies require good breadboarding techniques so you may have other problems even if the chip is functioning properly. In particular the critical loop areas must be kept small. See the typical layout in the datasheet for guidance.

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  • \$\begingroup\$ If we want to test it with resistor as dummy load, what is ideal value to test? And how you got output voltage? Is it mentioned in datasheet? Thanks. \$\endgroup\$ – Electroholic Jan 4 '16 at 16:38
  • \$\begingroup\$ A reasonable dummy load would be an 8.2V 1W Zener diode. This supply is a constant current type so I took the current you picked (190mV/2\$\Omega\$ = 95mA) and multiplied it by the 10K to get the output voltage (not counting the 190mV across the resistor). The 190mV VFB reference voltage is straight from the datasheet. \$\endgroup\$ – Spehro Pefhany Jan 4 '16 at 16:47

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