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So, I purchased a NJM2360D boost converter from Mouser. Using two 6V batteries in series to create a 12V supply, I'm trying to obtain a 40V output.

The "typical application" circuit from the datasheet is shown below: typical boost application

Can you guys offer any insight into the design of such a circuit?

  • How are the capacitor sizes chosen?
  • What size inductor will I need?
  • What type of inductor will I need? (when I try to find a simple "inductor", there are many options)
  • What does the voltage at pin 5 do? How do I select the resistors for the voltage division?

Any help would be greatly appreciated!

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  • \$\begingroup\$ The datasheet avialable via Mouser is fairly useless. I suggest you look on the NJR website for application notes or other design information. I suspect that the ratio of R1 and R2 will set the output voltage. \$\endgroup\$ – Peter Bennett Dec 12 '16 at 3:52
  • \$\begingroup\$ @PeterBennett well, that is all the information NJR provides as well. Out of luck. \$\endgroup\$ – Joshua Granger Dec 12 '16 at 4:34
  • \$\begingroup\$ google njm2360 , an ok-ish datasheet right at the top... \$\endgroup\$ – Spoon Dec 12 '16 at 8:00
  • \$\begingroup\$ njr.com/semicon/PDF/NJM2360_E.pdf gives the performance and more importantly (?) the block diagram that confirms R1 and R2 set the output voltage. \$\endgroup\$ – Spoon Dec 12 '16 at 8:07
  • \$\begingroup\$ Do you understand how boost converters work? I mean how far down the road are you because, any answer should consider your current knowledge without going right back to ohms law. \$\endgroup\$ – Andy aka Dec 12 '16 at 10:51
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The Texas Instruments MC33063A appears to be an equivalent to the NJM2360D and, has a much more informative data sheet containing PCB layout guidelines and formula tables for all main components. It also contains a detailed design procedure for boost and buck operation.

When it comes to questions about capacitors and inductors generally used for boost or buck regulators, ANY source of information from ANY recognized supplier of switching regulators will be as good as each other. For instance, if you look at Linear technology, they are very good at delivering part names and numbers in the vast majority of their switching regulator circuits and, generally speaking, what is usually good for one boost regulator operating at a specific frequency will be good for any other.

So if you don't understand how an inductor value is chosen, you might not expect the data sheet to help you there - you have to go out and google stuff but, it's worth looking at LT's data sheets because, in the main, I find them to be much more useful in this situation. Maybe other folk will also name other suppliers who provide such information readily to hand.

It's also worth going to TI's website and seeing if the MC33063 is available as a design in their webench - if it is then you should get some great knowledge just by using it.

Pin 5 attempts, via the feedback to maintain itself at 1.25 volts. Hence the circuit in your question appears to be a 30 volt regulator because 1.25 volts across 2 kohm sets a current of 0.625 mA flowing - this drops 28.75 volts across the 46 kohm resistor and therefore the voltage at the top of the 46 kohm is (28.75 + 1.25) volts.

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  • \$\begingroup\$ I got it working pretty damn amazingly. I appreciate your assistance. \$\endgroup\$ – Joshua Granger Dec 13 '16 at 8:09
  • \$\begingroup\$ Good man and well done. \$\endgroup\$ – Andy aka Dec 13 '16 at 8:40

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