LM3421: Want to use the LM3421 at 100% output without dimming.

MinKyu Kim

Prodigy 100 points

Part Number: LM3421
Other Parts Discussed in Thread: LM3423, LM3423BS2LYEV

Tool/software:

Hello, Ti teams.

I intend to drive LEDs at 48 V and 1.2 A output via the LM3421 from a 24 V, 2.5 A input.

The LEDs are connected in series (15 LEDs × 2.8 V Vf = 42 V total).

I want to maintain 100 % output at all times without dimming, and I’m wondering if using the configuration shown in the attached schematic will cause any issues.

I have purchased the LM3423 EVB for testing, but the LEDs didn’t turn on unless a PWM signal was applied. Is a PWM input mandatory?

22N02_MODULE_V00.pdf

2 months ago

0 Hailee Xu 2 months ago

TI__Genius 10080 points

Hi MinKyu,

which pin do you mean for this PWM signal input? And are you using this board? AN-2011 LM3423 Boost 2 Layer Evaluation Board (Rev. A) Thanks!

0 MinKyu Kim 2 months ago in reply to Hailee Xu

Prodigy 100 points

Yes, that’s correct. I wanted to use the LM3423BS2LYEV/NOPB to drive my LED PCB.

I read the datasheet and user guide and confirmed that it powers the LEDs.

The PWM input via the BNC is only for dimming, and without a PWM signal the LEDs remain continuously on.

What I’d like to do, however, is modify the setup so that the output voltage is fixed at 42 V.

Power management

Power management forum

LM3421: Want to use the LM3421 at 100% output without dimming.