Buck Converter for IBB Configuration with high efficiency and low ripple at light load

Hello

I think that almost any buck can be used as IBB.

But in your case I don't think that a buck is a good fit.

As you mentioned, at light load the converter will fold back frequency to give

high efficiency, but you nee constant frequency.  If you use FPWM then the 

frequency will be constant but the efficiency will be poor.

If the load is very light, such as the 10mA you mentioned, then the frequency

will be low and may not interfere with the AM band.  You can see some curves

for frequency vs load in some of our buck data sheets.

The best way to evaluate would be to use the EVM for a given device.

Otherwise you may need to go with a charge pump.

I will forward this post to my colleagues to see if they have any other suggestions.

Thanks

Hello Frank, thank you for the help.  The input voltage is 5.4V and all of the automotive grade inverting charge pumps have Vin(max) = 5.25V.  I limited it down to a few bucks that have the best light load(10mA) efficiency. Those are the three devices I mentioned in my initial post.

Maybe there is a different buck converter that I missed? Or, is there a different topology besides the inverting charge pump, buck-boost inverters (the one automotive grade buck-boost had poor efficiency @~10mA), and buck in IBB that could work for my application?  

Best,

Alex

And frankly, they already have the inverting charge pump in their system, so I do not think they'd want to switch to our inverting charge pump unless it had way better efficiency and less ripple.  Besides us not having any automotive grade inverting charge pumps for their design, I figured that pitching a buck that allows for wider input/output range would be best in case they need to modify their system. I'm curious to see what your colleagues can think of. 

Hello

You might look at the LM63615-Q1.  It should have OK efficiency in an IBB at light load in PFM.

But you would need to check on an EVM if it is OK.

When my colleagues return I will ask them for more ideas.

Thanks

Frank,

In general, when using a standard buck in IBB, does the efficiency or ripple decrease?

Hello

Yes, in general the efficiency will go down when converting a buck to IBB.

And the ripple will go up.

The hard question is how much they will change for a given case.

Thanks

Okay.  And, if the standard buck in IBB configuration is the best option, are there any that will work in my application that are still in stock?

Hello

I will need to check with our Marketing team to see what is in stock at this time.

I will try to get back to you as soon as possible.

Thanks

Hello

Base on some feedback from my colleagues it looks like the LMR36503-Q1 is your best bet since it is in stock.

The best thing to do is to get an EVM and test it out.

Thanks