LM3495EVAL: LM3495EVAL

adjagbe abdoul

Part Number: LM3495EVAL
Other Parts Discussed in Thread: LM3495

Hello,

i 'm working with the LM3495 EVALUATION BOARD and i'm trying to limit the current on my board

i saw in the dadtasheet the calcul of Rilim but when i choose 8A as my current limit but after all my calcul i found Rilim = 1K5

but during my test there are no limitation.

Do you have any idea of what i should do ??

thank you for help

over 5 years ago

0 JohnTucker over 5 years ago

TI__Guru**** 191445 points

Adjagbe,

What current limit are you seeing in your test? I calculate 8.82 A with 1.5 kohm. Any other modifications to the EVM?

0 adjagbe abdoul over 5 years ago in reply to JohnTucker

Prodigy 150 points

John Tucker,

i'm not seeing any limitation in my test, i had the same result as yours but i changed the RFb1 so i can have 3.7V as output with 51K resistor

best regards,

Adjagbe

0 JohnTucker over 5 years ago in reply to adjagbe abdoul

TI__Guru**** 191445 points

Adjagbe,

How are you testing it? What type of load are you using? I may have to order an EVM to check it.

0 adjagbe abdoul over 5 years ago in reply to JohnTucker

Prodigy 150 points

John,

How are you testing it?

I'm using a probe to check the current on the oscilloscope

What type of load are you using

i have 8 LEDS 3.7V for 1A each

i need to limit the current because my LED absolute rating in curent is 1.1A

best regards

adjagbe

0 JohnTucker over 5 years ago in reply to adjagbe abdoul

TI__Guru**** 191445 points

Adjagbe,

Can I see the waveform? What is your LED part number?

0 adjagbe abdoul over 5 years ago in reply to JohnTucker

Prodigy 150 points

hello John,

I made a new set up to test my theory:

i took a new evaluation board and try to limit the current at 1A so i use as Rilim=500mOHM, that work perfectly

-since i want to have an output votage of 3.7V with 12V as a Vin,

i changed the Rfb2 = 51.3kOhm with the current limitation at 1A with a load of 2 Ohm, i don't have the limitation at 1A i got 2.24A

I don't understand how the Rfb2 modification can impact the current limitation.

best regards,

Adjagbe

0 JohnTucker over 5 years ago in reply to adjagbe abdoul

TI__Guru**** 191445 points

Adjagbe,

The current limit is low side valley detect. The average (load) current is the valley current plus one half ILp-p. ILp-p = (Vout/Vin)*(Vin-Vout)/ (Fsw*Lout), so the maximum load current at current limit will vary with Vout, and any of the other variables such as Vin, Few or Lout.

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LM3495EVAL: LM3495EVAL