Please Help ID this part - LED Breathing Effect

The following part is used in a 3 V LED circuit, and I believe it is the part that is responsible for creating a breathing effect.
I’ve searched high and low, but cannot find it. Any ideas?

Welcome to the Technical Forum. I have not been able to identify this part. Though I am not the only person that is checking the forum posts. Someone else might be able to jump in and identify this one for you.

Thank you for checking!

Hi bitter.comings0v,

The FAN5646S700X and FAN5646UC00X have this capability.

Hello @bitter.comings0v,

Please elaborate. What is meant by the term breathing?

Until then, here are a few items for your consideration:

First, be sure to add an appropriate series current limiting resistor:

Second, look for the keyword “Arduino LED flicking”. A microcontroller such as the Arduino can be used to create a wide variety interesting of LED patterns.

Best Wishes,


Thank you for the recco, will definitely check these out. Thanks!

Hi APDahlen. The term “breathing” is also interchangeable with “fading”.
We have a 3V battery source, powering a 3V, 20mA red LED. This other component interest between the battery and the LED provides a fading-in-and-out effect to the LED. The pulsing fading effect ramps up and down with a short off period. The whole period is about 3.5 seconds.
An Arduino of any type would be overkill for this application.

1 Like

Unfortunately, Fairchild (acquired by OnSemi) no longer makes them. Rochester Electronics, who specializes in stocking obsolete parts still stocks them, as my links above show.

If you need a still active part at a reasonable price and in a fairly small form-factor, then going with a small package microcontroller, such as the PIC10 or ATTtiny4,5,9,10 are a reasonable alternative option. They are pretty inexpensive, though one has the development cost to write the code and program each part. Flexible purpose MCUs such as these seem to be the reason application specific parts such as the FAN5646 seem to be disappearing.

1 Like


You are correct a microcontroller is overkill. But @David_1528 is also correct. The smallest 6-pin microcontrollers are a good value. You will have full control of the LED and you will be able to add additional functionality such as the RGB LED.

Please let us know the path you have chosen for your application.



P.S. If you are new to electronics, you may want to consider the 555 timer. But then again, the microcontroller may be in the same price category.