Re: Switching power supply question

NoName · 2008-02-25T02:24:43+00:00

[...]That should be caught in incoming inspection.It is never a good idea to use typical values in a design. From thedatasheet:"The LP2985 was designed to work with ceramic capacitors on theoutput to take advantage of the benefits they offer: for capacitancevalues in the 2.2 uF to 4.7 uF range, ceramics are the leastexpensive and also have the lowest ESR values (which makes them bestfor eliminating high- frequency noise). The ESR of a typical 2.2 uFceramic capacitor is in the range of 10 mohm to 20 mohm, whicheasily meets the ESR limits required for stability by the LP2985."It sounds like they intend the part to be used with low ESR caps.I'm sure you could require a guaranteed performance spec in apurchase contract if you were willing to pay for it.Anyway, this was just an example to show it is possible to improvethe ESR performance without requiring an extra pin with externalfilter components.This is an implementation problem in the design. Obviously it issomething you check before committing a part to production.[...]I checked the parts in Digikey before posting. Certainly the priceis high - that's what you pay for in a monopoly. However, the partis not affected by ESR, and it does not require an extra pin withexternal filter components. So a clever design might get around thepatent and give the same results.Your complaints about LDO's are well known. You spoke of rollingyour own when needed. Any chance you could post a schematic sowe could see how these problems are solved?

Feb 25, 2008 27 Replies

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RST Engineering (jw) 18 years ago

What's a PL500? I fixed TVs all the way through high school and never ran across that device in a few hundred sets I worked on.

Jim

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Tim Williams 18 years ago

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Nah, the output tubes are heated normally - the input tubes come on later.

Tim

-- Deep Fryer: A very philosophical monk. Website @

formatting link

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Joerg 18 years ago

In Europe that was done with auto-windup relays. Klick, rat-tat-tat-tat ... clunck. The only mercury found in a typical household was in the flu thermometers, and only for a while.

Then you aren't 'sposed to touch that Syrah yet. Got to wait until the year 2024.

Regards, Joerg http://www.analogconsultants.com/

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Joerg 18 years ago

It's a European H-flyback tube. Early sets had the PL36 which I liked better. It lives on in the audio world as the EL36. E-types had 6.3V filaments, P-types where all 300mA so you could connect the filaments in series.

For color sets it wasn't powerful enough and those used the PL509, later the PL519. Those made excellent shortwave power amps.

Regards, Joerg http://www.analogconsultants.com/

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Jim Thompson 18 years ago

life

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OK. I'll just have Chardonnay ;-)

...Jim Thompson

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krw 18 years ago

That there should *be* an incoming inspection? Incoming inspections went out with buckle shoes (and six sigma).

Keith

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MooseFET 18 years ago

There really still is "incoming inspection". It is now spread between the receiving clerk and the assembler. If completely wrong parts are delivered of the holes don'y line up, the fault will be caught before the assembly is finished.

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krw 18 years ago

Well, if that's considered "inspection"...

Keith

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