MP3301 PWM over 1.4V

Lighting Solutions
1

I am trying to run a PWM at 1KHz 33% duty, when I run the EN pin at 3.3V there is a lot of noise from the inductor (I assume).
However when I run the EN pin at less than 1V with 100% duty (Same average voltage) the noise isnt there.
LED intensity similar so it sems to be operating the way you would expect.
The MP3301 doesnt seem to like going above 1.4V, anybody else had simlar issue? What am I missing?

2

You did something wrong, get a Eval board

3

Thank you fo ryour kind reply,

Do you know of any design application notes on this product range?

4

Hello,

Eval boards are a great reference for a working system and are used as tools to evaluate and debug and IC. But I think it would be productive to ask the following:

Do you happen to have a schematic to provide? Input voltages, output voltages, the number of LEDs you are driving would also be good to know as well.

For reference, here is one of the typical applications of the MP3301:

image
image1013×594 50.8 KB

If you think noise is coming from the inductor, please verify by viewing and sharing waveforms of the input, output, and switch node. If the inductor is the source of this noise, then check the sizing using the formulas from the following reference article:

Boost Converters (Step-Up Converter)

Also, as for the varying behavior given different EN pin voltages, please see the following:

image
image888×97 24.9 KB

Let me know how things go.

Best,
Krishan

5

Hi,

5V input, 22.4V - 25.6V out, 15mA, Driving 8 LEDs in series.

I will check the inductor sizing again with your reference.

Thanks
Mark

6

Sounds good. If this doesn’t fix the issue, then feel free to send in a schematic for review when you find the time.

Best,
Krishan