Re: gEDA-user: powermeter power supply update

[Joerg <joergsch@xxxxxxxxxxxxxxxxxxxxx>]

DJ Delorie wrote:
> I promised an update to this, and here it is.
> 
> I got the LM25575 eval board and wired it up to the powermeter board's
> bulk supply, so I could compare theirs to mine side-by-side (kinda the
> whole point, yes?).
> 
> A pin-by-pin comparison of the two supplies showed that most pins were
> acting the same, except one - the FB pin (feedback - it's the output
> of the error comparison amplifier) had a clocked signal on it on my
> board, but was a steady DC on theirs.  None of the nearby pins had a
> clock on it, the solder joint was good, the PDF showed no reason why
> there would be a clock on it.  Diagnosis: bad chip.
> 

FB would be the input of the error amp:
http://www.national.com/an/AN/AN-1578.pdf

And yes, if the FB pin spits out pulses the chip is busted.


> So, I replaced the chip with the new one I had ordered.  Now it works
> fine.
> 
> As an aside - the ENC28J60, R8C, FTDI232R, and two ADE7753 chips, use
> a total of 164 mA.  The board holds 16 ADEs so 14 x 5 mA is another 70
> mA, total 235 mA - well short of the expected 600 mA worst case.  The
> ENC28J60 is spec'd at 250 mA all by itself.
> 

Maybe you can get carbon credits for the saved 365mA :-)

-- 
Regards, Joerg

http://www.analogconsultants.com/



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