# How can the output current be programmed in the LTC3649 step-down regulator?

I use Analog Devices' LTC3649 regulator as a step-down regulator. It is said that there is a programmable output current in the datasheet, but I have no idea how to do this. Does anyone have an idea or information?

I'm making a regulator with adjustable output current and output voltage.

• youtube.com/watch?v=CIGjActDeoM here an regulator is setup with voltage and current adjustment options. Jun 2, 2021 at 9:19
• thanks for reply. This content is not exactly what I was looking for, but it was useful content for me. Jun 2, 2021 at 9:51

If you read the datasheet of the IC, it isn't really current regulation but current limiting that is possible. See page 9:

"Output Current Monitoring and Regulation The LTC3649 has the ability to accurately sense the average inductor current without the use of an external sense resistor. The IMON pin output current is 1/40000th scale of the inductor current. ... In addition to simply sensing the inductor current, the LTC3649 can also be programmed to regulate the aver-age output current limit. The regulator will limit the peak inductor current if it senses that the voltage on IMON has exceeded 2V."

As a general remark, when you are regulating voltage into a variable load, you can really only do one of two things:

1. try to keep voltage at some fixed value (up to the maximum current that the device will supply, after which you are forced to reduce voltage to prevent damage). This is voltage regulation.
2. try to keep current constant, up to some maximum voltage, with the same restriction. This is current regulation.

You can do one or the other at any given time, but not both.

• Thanks for the explanation. Do you have a regulator suggestion where I can do both? Or is something like this possible? Jun 2, 2021 at 10:13
• As I said, you can do either, but not at the same time. Which is logic if you think about it. The load is varying and Ohms Law applies. For any voltage a current will flow based on the value of the load at the instant. What are you actually trying to achieve here? Jun 2, 2021 at 10:16
• I am a student and I am currently doing an internship. I am trying to make a regulator with internal current regulation and internal voltage regulation for the company. I did research on Analog Device to find an internal current adjusted regulator. I found LTC3649 and LT8613 regulators but I guess I misunderstood. Jun 2, 2021 at 10:37
• I think you need to clarify what behaviour you want. In this case things are a bit confused because the word regulation is being used interchangeably with limiting. They are not the same thing. Jun 2, 2021 at 10:44
• I get it, I'll go over it again. thanks again for the explanation. Jun 2, 2021 at 10:49