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General Question:

I would like to integrate a specialized chip that requires symmetrical power +15, 0 and -15 V to operate on a 0 V (GND) / +5 V (VCC) board I designed. If possible, I would also like to support 3V – 5.5 V power supplies.

I am pretty sure it should be possible, but I do not know how to do that (I have very little knowledge in electronics) and searches turned up nothing.

More precise question:

The part I would like to use accepts from ±12V to ±22V power supply, so the supply does not need to be exactly 15 V. Also, the part includes an internal precision 10 V reference, thus, the power supply of the chip does not need to be outstandingly stable. The 5 V supply I have on my board is stabilized.

Below are the characteristics of the part given by the manufacturer:

Supply: ±22V Input Current, Continuous: 40mA Input Current Momentary, 0.1s: 250mA, 1% Duty Cycle Common-Mode Input Voltage, Continuous: ±40V

I am mainly interested in learning, so any explanation will be highly appreciated. Thank you very much for reading me and for your guidance.

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  • \$\begingroup\$ I forgot to mention it, plus, it is not really a question, but I would be interested in using preferably cheap parts. \$\endgroup\$
    – PeterG
    Commented Dec 27, 2013 at 17:37
  • \$\begingroup\$ Can you start with a +15V supply input, rather than +5V? Or even a little bit higher, +24V wouldn't be too high. If you can make that choice, that open some options, which make the design of the power converters simpler. \$\endgroup\$ Commented Dec 27, 2013 at 17:40
  • \$\begingroup\$ @NickAlexeev Thanks for your reply. Actually, I would very much avoid resort to this solution because, eventually, the whole system will be battery powered. \$\endgroup\$
    – PeterG
    Commented Dec 27, 2013 at 17:49
  • \$\begingroup\$ What will be the battery voltage? \$\endgroup\$ Commented Dec 27, 2013 at 17:52
  • \$\begingroup\$ Selected battery voltage is 9 V currently (regulated down to 5 V) but shoud evolve to 4.5 (regulated down to 3.3 V). \$\endgroup\$
    – PeterG
    Commented Dec 27, 2013 at 17:54

2 Answers 2

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Because it's xmas I'd be looking for an off-the-shelf-and-very-lazy solution and my 1st port of call would be Traco and the TMA series of power supply modules.

The TMA 0515D can provide +/-15V (isolated) from a 5V dc supply. It's a 1 watt "solution" and can deliver up to +/- 35mA to your load at an efficiency of about 80%. You can also get a +/-12V output version too.

It's about 2cm long, 1cm high and about 0.7cm wide. It's an unregulated version so it does need a fairly constant 5V power supply but there are others in the range that work across a variety of input voltages and some provide output power up to over 30 watts.

I'm beginning to sound like a sales man now!!

They cost £3.50 from Farnell

If you want this power supply to work with input voltages from 3V to 5.5v you would need to introduce a boost-buck converter to produce a stable 5V rail to feed it. Alternatively use a version of the Traco with a 12V input (TMA 1215D) and use a 12V boost(only) converter to power it from 3V to 5.5V. I would go this route because it's simpler (and probably cheaper) to design a boost circuit than designing a dual flyback switching converter.

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  • \$\begingroup\$ Nice ! I have seen TRACO also provides 2 and 3 W parts, which would be able to supply the required current. However, they are really expansive ! \$\endgroup\$
    – PeterG
    Commented Jan 1, 2014 at 13:51
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You could build a boost converter, but it might be hard on your batteries: 250ma @ 15V will require at least 750ma @ 5V, and therefore you ought to expect an amp from the batteries. If you want decent battery lifetime with this part on the board give it its own battery pack with a buck converter producing 5V for the logic.

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  • \$\begingroup\$ The specs say : Current Momentary, 0.1s: 250mA but also : Continuuously : 40 mA. So I would only need to provide 40 mA or so. What would happen if I go with a solution capable of providing 80 mA? The part is a 4-20 mA current loop reciever. Can I just go along with a capacitor ? \$\endgroup\$
    – PeterG
    Commented Jan 1, 2014 at 13:50

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