Led2001

HKIM.21 · ‎2021-03-23

Hi.

LED2001 driver is chosen for my design.

The eDesignSuite tool was used for my design.

My goal is to use the LED with Vf of 3.0V and If of 3.0A.

And, The input voltage of LED driver range from 3.5 voltage to 4.2V.

The voltage across the feedback resistor is measured to 800mV. According to the datasheet, its minumum voltage at FB pin is 900mV. I wonder why actual Vfb is lower than its minimum voltage.

Peter BENSCH · ‎2021-03-24

The datasheet of the LED2001 gives a feedback voltage of typically 100mV, min 90mV, max 104 (110)mV.

So if you measured 800mV in the design shown, the current through the measuring resistor is calculated to be 0.8 V/0.0332 ohms = 24.1A. Are you sure that Rs has the current value 0.0332 ohms?

Regards

/Peter

In order to give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.

HKIM.21 · ‎2021-03-24

Lol. It was typo..The measured voltage is 80mV, not 800mV.

Peter BENSCH · ‎2021-03-24

I had already suspected that. However, an input voltage of at least 3.5V is very close to the forward voltage of the LED. Please do not forget that both the internal FET and the coil have an ohmic resistance. It can therefore become difficult to drive the full 3A with such a small voltage difference.

What do you think about measuring the voltage curve on the shunt with a scope?

Regards

/Peter

In order to give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.