Author Topic: Switching supply PSA...  (Read 1135 times)

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Offline T3sl4co1l

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Switching supply PSA...
« on: March 18, 2016, 06:28:09 pm »


http://imgur.com/gallery/SoYtht4

;)

Feel free to write your own of the (or related) memes!

Tim
Seven Transistor Labs, LLC
Electronic Design, from Concept to Layout.
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Offline Rerouter

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Re: Switching supply PSA...
« Reply #1 on: March 18, 2016, 09:25:15 pm »
I'm sorry, but i don't really understand,

The chip from its datasheet appears to have decent specifications, and the layout doesn't look that bad?
Well apart from 35V caps used on a 40V max chip.
 

Offline T3sl4co1l

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Re: Switching supply PSA...
« Reply #2 on: March 19, 2016, 10:44:32 am »
Decent in 1980, perhaps!  It's dreadfully slow, barely ultrasonic; the control scheme is undefined (you have an "oscillator" block with apparently some means of current sense), the behavior is hysteretic so not only is the ripple massive from the low operating frequency, but it's several times worse due to pulse skipping and chaotic limit cycles; shall I continue?

All of the alternatives listed are modern CMOS devices, with operating frequencies up to a few MHz, and excellent stability, efficiency, and current limit performance.  You will literally save more on capacitors and inductor alone than the chip cost.

Tim
Seven Transistor Labs, LLC
Electronic Design, from Concept to Layout.
Need engineering assistance? Drop me a message!
 

Offline xygor

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Re: Switching supply PSA...
« Reply #3 on: March 19, 2016, 10:54:12 am »
Is that the stupid chip with the error amp gain inversion when the common mode voltage range was exceeded.  (i.e. negative feedback turned into positive feedback.)  I got burned by that figuratively and the parts literally.  Die! mofo Die!
 

Offline T3sl4co1l

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Re: Switching supply PSA...
« Reply #4 on: March 19, 2016, 10:55:03 am »
Dunno, but that's characteristic of many older chips!

Tim
Seven Transistor Labs, LLC
Electronic Design, from Concept to Layout.
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Offline SeanB

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Re: Switching supply PSA...
« Reply #5 on: March 19, 2016, 05:03:02 pm »
1 billion ultra cheap and nasty mobile cellphone chargers use it though. I have repurposed a few as cheap and nasty buck converters to charge batteries, or as simple LED drivers for a single LED. Put a decent cap and inductor on them and they do work well enough.
 


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