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TL7660 CMOS VOLTAGE CONVERTER Caveats?

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Honduras

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I realize it is relatively low voltage, but so am I.

Suppose I have 18 volts in from a bridge rectifier. Do you think I could split that between an LM7805, with full filtering, and an LM7905 with the same filtering? Am I getting too close to the lower edge of what the regulators can handle?

I've never used one of these before and have no idea.

If I could find a 'Rail Splitter' for this range, would it be better? I think I would have to use a 15 volt regulator and put the rail splitter in the output circuit.
 
What are you powering that needs a dual polarity power supply?
ANY opamp will work from a single positive supply if it is biased correctly.
 
What are you powering that needs a dual polarity power supply?
ANY opamp will work from a single positive supply if it is biased correctly.

It's not a bare Op Amp. It is part of a special purpose IC. Can't even remember which one, but I think it's part of an LED display driver. I'm not really comfortable in that area, so I' trying to keep it as simple as possible . . . for my comfort.
 
You are trying to make a positive and negative supply from a single supply of 18V?
And you can't remember which IC needs it?

The datasheet for the 7660 IC shows its maximum allowed supply voltage is much lower than your 18V and also shows that its maximum negative output current is about only 20mA.
 
You can easily make a rail splitter with a pair of equal resistors driving an opamp configured as a voltage follower.

The choice of opamp begs the question, how much unbalanced current will your load present to the midpoint?
 
Using it in aa voltage divider configuration won't work? I ws yhinking of connecting the
You can easily make a rail splitter with a pair of equal resistors driving an opamp configured as a voltage follower.

The choice of opamp begs the question, how much unbalanced current will your load present to the midpoint?

That's a big question. I've been assuming that the negative leg would draw more current than the positive leg because the only difference between the two legs, would the resistance added by the TL7660. Or did I get that backwards?
 
My suggestion of an opamp as a rail splitter was to replace the TL7660.

What are the voltage and current requirements of device you are trying to power?
 
There is the TLE2426 precision rail splitter, to generate "virtual grounds" which comes in a small 3 pin package...just saying.
 
Its spec's are pretty good when its loads are 10mA but the spec's deteriorate at 20mA.
 
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