Hello!
I am designing an intricate power network for my next board and I need some help about using fly-buck converters and choosing suitable transformers.
I need the following lines:
1) 3.3 V main line (max 600 mA)
2) 1.8 V line (max 20 mA)
3) 3.3 V isolated line (max 160 mA)
4) 3.3 V isolated line (max 20 mA)
5) four isolated sections, each with a 12-24 V line (max 50 mA @12 V) and a 3.3 V line (max 300 mA).
All isolated lines should be separately isolated with each of the other ones, My power source will be 24 V or 48 V.
I can surely:
- derive line 2) from 1) with an LDO
- derive 5) 3.3 V lines from 5) 12-24 V lines
Hence, I finally have to generate a stable 3.3 V line, two stable 3.3 V isolated lines, and four 12-24 V "not stable" isolated lines.
My first thought was to use a single LM5160 in order to generate all of those outputs, but I would need a somewhat strange transformer, something like 1:4:4:4:4:1.1:1.1, or something like that. And I could not find one. Besides that, our estimated annual usage is quite low (< 100 pcs), so I don't think I can afford the possibility of generating a custom part. But if you know of someone who can help me, your help will be much appreciated.
Moreover, it is not clear to me whether the current rating of LM5160 (and, by the way, of all regulators) is somewhat correlated to the output voltage. In other words: if I need, say, 10 W at my output, I could, in principle, choose to have a 3.3 V, 3 A output line, or a 24 V, 417 mA output line. Both lines can give the 10 W I need, but the first one has a current rating too high for LM5160 (rated 2 A), while the second one can easily be managed by the same LM5160. Is it correct? Or is there something to worry about, when dealing with higher voltages and lower currents?
Another, more practical, solution for my issue could be to use a couple of LM5160A.
The first LM5160A should generate the four "high voltage" isolated outputs, with the non-isolated line set at 10 V, in order to power VCC of both LM5160A. The isolated outputs could be generated by means of Wurth 750315038 transformer and would go to 23 V. A buck converter (such as LM43602, found with WeBench) would then generate the 3.3 V output.
The second LM5160A should generate the main 3.3 V output and the two 3.3 V isolated outputs, which perhaps could be more stable by introducing an LDO and/or a buck converter such as LM43602 again. In this case, I would need a transformer with turns ratio such as 1:1.2:1.2 or similar, in order to take into account the diode drop on the isolated sides. I found something which could be suitable, but as they are not designed for LM5160 I'm not sure if they can do the work well. The part numbers are GT06-122-053 from Ice Components and T60403-F5046-X100 from Vacuumschmelze. Can you give an advice about them?
Thanks in advance for your help.
Stefano
