VOGONS

Buck Regulator Controller LM2636 - Alternatives?

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First post, by smesgr

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Hey everyone,

My K6 MVP3 system did hang on running 3D Mark '00. After reset the system did not boot again. POST card showed "-- --". After measuring the VCC with only mV something was off.

It turned out the K6 died and took LM2636 with it OR the other way around. Sadly the LM2636 isn't that easy to come by. There are several offerings in the US which either have insane minimum order value of >200$ or very unfavorable shipping condition.
The controller is afaik used in good chunk of mainboard end '90 to early '00. The part is not produced any more by NS/TI - thus the stock will likely try out.

I finally found Aliexpress offering which look very shady https://de.aliexpress.com/item/1005001362762897.html. Even through claimed original the part don't look original but at least the chips works for me. The system is up and running again.

So long winded introduction to the question. What are the alternatives? Are there any pin compatibles options?

PS. booting with an dead CPU could result into VCC2 is not provided by the LM2636. This took me ages to figure out. I put my money on the caps or mosfets - but they are running fine.

Reply 1 of 2, by rasz_pl

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I dont see whats shady about that listing, if it works it works, I wouldnt worry about it

https://github.com/raszpl/FIC-486-GAC-2-Cache-Module for AT&T Globalyst
https://github.com/raszpl/386RC-16 memory board
https://github.com/raszpl/440BX Reference Design adapted to Kicad
https://github.com/raszpl/Zenith_ZBIOS MFM-300 Monitor

Reply 2 of 2, by smesgr

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I doubt the originality of the chips. Either they are used NS chips were they removed the original markings and reprinted new markings on them (thus is a lottery if your chip is good or not) or are reproductions chips.
If they are reproduction chips it is unclear if every feature is available. The chip design implements some feature like over voltage protection - they may not have reproduced or have other behaviour. This could be crucial if a board design relies on certain tresholds.

I have no issue with reproductions but if it should be stated and ideally there is a data sheet which list all of the specifications of the reproduction.

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