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# A couple of questions for your ADD5211 LED driver

Our customer is evaluating with your ADD5211 LED driver.

So he just tossed a couple of questions as following

He designed 2 ganged on 2 ch ,and each channels pull 3 LEDs.

Vf=1.8V LED

Q-1

Can your ADD5211 drive as current dimming control not PWM control?

He needs the dimming fuction as current control.

PWM bring thr flicker for LED on-off.

This flicker make bad for his products.

Q-2

If he put the over 22uF for Cout on your datasheet page-15, then what trouble coming? Growth ripple noise?

Q-3

As for thr PWM frequency,

when 300Hz:dimming=1000:1

So when 25kHz:dimming=?:1, =1000:1 correct?

This is brought from page-1 on your datasheet FEATURES.

Q-4

If he put the frequency of PWM from 300Hz to 20kHz, then he just found that the charge pump voltage become growth high.

Why this result have comin?

Anode voltage of LED(as VLED)

duty 0:900, VLED=4V

duty 1:900, VLED=38.6V

duty 2:900, VLED=37V

duty 3:900, VLED=28.2V

.

.

.

duty 8:900, VLED=9.6V

But when the PWM freq=300Hz, VLED=4V all.

Thanks Kaos

Parents
• Hi Jon,

As for your answer for my question-1,

Our customer is studying with your ADD5211 as drive current control.

So from your spread sheet past you enclosed, he has tryed to calcurate as my enclosed.

Look at the sheet "case of our customer"of "ADD5211 case study.xlsx".

Min currnet is showed 15mA.

Question:

Can we control to drop less than 15mA?(How can we control 0mA to 15mA?)

Customer have used 3.3V power source.

Thanks Kaos

• Hi Jon,

As for your answer for my question-1,

Our customer is studying with your ADD5211 as drive current control.

So from your spread sheet past you enclosed, he has tryed to calcurate as my enclosed.

Look at the sheet "case of our customer"of "ADD5211 case study.xlsx".

Min currnet is showed 15mA.

Question:

Can we control to drop less than 15mA?(How can we control 0mA to 15mA?)

Customer have used 3.3V power source.

Thanks Kaos

Children
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