There may not be a measureable current flowing into the output.
It's high impedance when its off I guess.
So it may drift up.
Is there a reverse protection diode across the reg that can leak?
What is the load on the output, is the 2k present?
Jan
It's high impedance when its off I guess.
So it may drift up.
Is there a reverse protection diode across the reg that can leak?
What is the load on the output, is the 2k present?
Jan
Just the board by it's self, connected to a 12v X 2 @ 50VA Antek toroid with load resistors to simulate in use conditions. There are no sources for the current to back feed into the regulator. And if you mean R211 across the output, it is mounted on the board so always in-circuit.
I have a few more LT1963's lying around so I think I'll build a separate regulator board to test...I'd kinda like to figure this out if I can.
Mike
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These don't require protect diodes so I didn't include them. The circuit design I incorporated was lifted straight from the data sheet.
Mike
Mike
I'm back...again. I assembled another LT1963 circuit using a board I hade made last spring for a 9 volt power source for guitar stomp boxes. It's the same stock circuit pulled straight from the data sheet, but with a slightly different layout, and no other circuit elements like PCB201 has...just a regulator by itself. And...I get exactly the same results, about .27 volts @ around 180 uA output when the shutdown pin is either left floating, pulled low by a 10k resistor, or shorted to ground. Is this an "undocumented feature" of this chip? Again, as I said before, I wouldn't expect this to cause any issues, but it just doesn't seem nominal to me.
Mike
Mike
That seems an imperfection of the IC. Pity as it is a good regulator.
Again a reason to use real switches at the AC side. True zero power/green. True nil technology 🙂
Again a reason to use real switches at the AC side. True zero power/green. True nil technology 🙂
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From my point of view it looks like a defective chip, maybe a counterfeit, I would probably consult it directly with the chip manufacturer, or try to buy it in another trusted store and replicate the issue. Datasheet specs <1uA on the output in the shutdown mode 😳
There is a real switch on the AC side...this is for the stand-by mode for which I don't anticipate any more than about four or five watts of "wasted" power. But is it really wasted if it is being used for a legitimate purpose?
Mike
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Actually...I tried three different chips, all from DigiKey so I'm confident they are the real deal, all got the same results.
Mike
@Michael Bean This is really bad, you can have defective chip and you should report it to the manufacturer and request an exchange and compensation 😉
It's hard to believe that three (3) chips from DigiKey in two shipments separated by almost a year with different date codes would be "defective" all the same way, and I'm sure that DigiKey isn't selling chips from unknown sources. I think it might be a minor flaw in the design that has never been caught, or maybe it is a manufacturing defect, I don't know. But in any case, I've use several of these in other circuits and have never had any problems, and this issue doesn't affect normal operation in use, so I think I'll just tie the shutdown pin high like I always have in the past and just use a MOSFET switch for standby mode.
Mike
Mike
Did you put in a mail to tech support? It may take a few days but generally you get an answer.
Something what I often do in cases like this is report a data sheet error (there's a link in the data sheet normally) explaining the difference between the data sheet spec and the actual operation.
That either gets you a thank-you for spotting the error, or why you seee what you see.
All free and quite satisfying.
But be short, to the point, no whining. Refer to section, figure, whatever.
Make it as easy as possible for them to understand what your point is.
Include schematic, part values, actual measurements and the conditions, the works.
Not a typical diyaudio post ;-) but a clear tech report.
Jan
Something what I often do in cases like this is report a data sheet error (there's a link in the data sheet normally) explaining the difference between the data sheet spec and the actual operation.
That either gets you a thank-you for spotting the error, or why you seee what you see.
All free and quite satisfying.
But be short, to the point, no whining. Refer to section, figure, whatever.
Make it as easy as possible for them to understand what your point is.
Include schematic, part values, actual measurements and the conditions, the works.
Not a typical diyaudio post ;-) but a clear tech report.
Jan
Thanks Jan, I may give that a try just to satisfy my curiosity. Since I have already used these successfully with the shutdown pin permanently tied high, I'll probably not wait for a response...I'm too far along in this project, and I want to git-er-dun!
Mike
Mike