Flyback transformer LM2577

Could you recommend a flyback transformer lm2577? the transformers indicated by Texas Instruments in the datasheet are all obsolete or unavailable, I would need one for a 12 volt input into the LM2577 and a 15± volt output.


I’ll see what I can find. What is your max load current on each rail?

The device connected to the output has a consumption of 15+ 150ma 15- 140ma, approximately

The device connected to the output has a consumption of 15+ 150ma 15- 140ma, approximately

Hi, I did not find anything like LM2577 with an output of -15v. We do still carry the LM2577 however. Please see link below, it is adjustable voltages. Thanks, Glenda

Hi @Frekkia,

This is a tough one. It looks like the Pulse PE-65300 shown on page 27 of the datasheet would work, based on the graph of Fig.45, but we don’t stock that one (it is still available from Pulse, but one must buy the full pack quantity of 165 pcs and lead time is 15 weeks).

Another possibility I found is the Bourns HCTSM80102AAL-E1. However, I am not confidant that it can handle the output current you require.

Wurth makes a part which would also likely work, the 750344704, but we do not stock it, so it, too, would require a special order and there would be a minimum order quantity. I have the datasheet for it if you are interested.

One other thing I found which might possibly work is the VP4-0860-R from Eaton. It is a configurable transformer with 6 coils all coupled together, but with flexible connection options.

With this part, you would parallel coils 1-12 with 4-9 to form the input coil. For the output, two series coils should be formed by tying pins 11 and 3 together along with pins 8 and 6. Then those two series coils should be connected in parallel by tying pins 2 to 5 and pins 10 to 7. Finally, pins 11,3,8, and 6 should all be tied together to form the center tap. In this configuration, pins 2,15 will be the +15V output and pins 10,7 will be the -15V output.

Configured this way, the primary side inductance would be roughly 87uH and the secondary side would be roughly 348uH, which is not too far off from the PE-65300.

Thanks @David_1528 I’ll try, I don’t understand a thing but where the first GND marks would be the connection with the switch use, right? 12-9


You are referring to a switch for turning on the 12V supply, I presume? Assuming that is the case, pins {12,9} (tied together) are the low, or ground side of the 12V input.

If you have 12V tied directly to {1,4}, then placing a switch between {12,9} and ground would power the input. Alternatively, depending on where this thing will go, you could tie {12,9} directly to ground, and put the switch between {1,4} and your 12V supply. The first is a low-side switch and the latter would be a high-side switch.

@David_1528 I don’t know if we talk about the same thing, I mean this!

Sorry, yes you are correct - the internal switch of the LM2577. It’s been a long day!

@David_1528 Yes I understand you :(… So it’s like I said? should the Ground be connected to the internal switch?

Yes, the Ground symbol (pins 12,9) should be connected to the Switch, pin 4 of the LM2577.