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Old 5th February 2007, 07:45 AM   #1
i-s is offline i-s  United Kingdom
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Default Pin compatible 7815/7915 replacements?

I have searched on this, but perhaps I have the wrong search terms...

I'm looking for pin-compatible TO220 (ie drop-in) replacement parts for 7815 and 7915. I have seen advice here to use LM317 and LM337 on small bits of veroboard, but my application is too space-limited to do this, and on paper that gives no improvements in regulation or output noise over the fixed parts anyway.

Any suggestions, or links to blatently obvious threads that I've missed?
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Old 5th February 2007, 07:01 PM   #2
Minion is offline Minion  Canada
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I don"t think there are any drop in replacements for those regulators not ones that will provide better performance...

becides the LM317/337 regulators (Which should be able to drop in with only a couple small changes to allow for a Diode and 2 resistors One of which can be mounted to the regulator as well as the Diode)

I suppose if you were in a Pinch you could use a Resistor and a Zener Diode as a regulator but it would not offer any improved performance......

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Old 5th February 2007, 07:17 PM   #3
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http://www.newclassd.com/index.php?page=70

You only have to wait for the 79xx variant and I do not know if those are planned... BTW I haven't used them so I can't comment on quality etc.

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Old 7th February 2007, 05:10 PM   #4
i-s is offline i-s  United Kingdom
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Thanks for that. Unfortunately my application is too space-limited for those. Guess I'll just not worry about it then...
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Old 8th February 2007, 04:12 PM   #5
cpemma is offline cpemma  United Kingdom
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As a pin-compat with 78xx (centre ground pin), the LDO LM2940 fits the bill, but they don't come in 79xx equivalents. And whether or not they're an improvement on 78xx, I've no idea.
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Old 8th February 2007, 04:26 PM   #6
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Default Re: Pin compatible 7815/7915 replacements?

Quote:
Originally posted by Isaac Sibson
I have searched on this, but perhaps I have the wrong search terms...

I'm looking for pin-compatible TO220 (ie drop-in) replacement parts for 7815 and 7915. I have seen advice here to use LM317 and LM337 on small bits of veroboard, but my application is too space-limited to do this, and on paper that gives no improvements in regulation or output noise over the fixed parts anyway.

Any suggestions, or links to blatently obvious threads that I've missed?
I think the reason 317/337 are preferred is because you can put a capacitor on the control pin which does make an improvement.
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Old 23rd October 2010, 06:39 AM   #7
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Lightbulb LM2990

Quote:
Originally Posted by cpemma View Post
As a pin-compat with 78xx (centre ground pin), the LDO LM2940 fits the bill, but they don't come in 79xx equivalents. And whether or not they're an improvement on 78xx, I've no idea.
LM2990
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Old 23rd October 2010, 07:31 AM   #8
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An old thread but still interesting as new parts are being developed. The current OnSemi MC7815 and MC7915 have much better specs than the original 78xx and 79xx series. The datasheet has been updated as a result of that.

Please compare the OnSemi MC78xxAC and MC78xxCTG and choose the type with the best specs for your application. They have different specs. This also counts for the negative variant of course.

Please note that the negative 15V variant that OnSemi produces has only 90 uV noise. That is way lower than 7915 types of other manufacturers. For example National's LM7915 has 375 uV noise ....

Always use output caps, certainly with 79xx and make sure the load draws some mA otherwise the output might be unstable. This is considered to be common knowledge but it is done wrong in many devices. A simple solution is to connect the power LED at the negative regulators output.
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Old 26th October 2010, 10:47 AM   #9
amc184 is offline amc184  New Zealand
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There is also the TL780, Texas Instrument's improved version of the LM78xx. There is no negative equivalent though. Voltage output is tighter, ripple rejection is better, but the noise is about the same.
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Old 26th October 2010, 04:05 PM   #10
macboy is offline macboy  Canada
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LM340T-05 is an example of an equivalent part number.

But if you look around you will find many many many variations of the "78xx" series, from many vendors. Not all are the same. No two are the same. Yet people lump them together, and base their opinions and advice on their (usually bad) experience with just one of them. You can find low noise 78xx series with good PSRR, good load regulation, and overall very good specs. You can also find downright crappy ones. Not all are equal.

Same goes for "5532" opamps. People tend to forget or ignore, inexplicably, that many different vendors produce "5532" opamps and that no two are the same, except for similar specs around noise, bandwidth, etc.
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