+5 to -5 charge pump thingie

Yeah,

My stuff is all low-volume, military these days so component cost isn't much of a concern.

Nice little part though.

Bob

Or just charge-pump off the flyback diode. I was doing that when you were still a kid. Heck, *I* was still a kid.

John

ROTFLMAO! all depends on the frequency. 50/60Hz, yes. 100kHz, no. Shit, PSRR curves go below 0dB at some frequency. for a TL064 its around

100kHz, as I discovered the hard way. RTF data sheet would have been easier - *if* they gave me a PSRR curve.

Cheers Terry

You can also use little wire croquet-hoop thingies to secure a toroid to the board, and then use them as secondaries, and rectify that.

John

I used that scheme to generate a nice regulated -5V in several of the GenRad portable testers.

And I'm still a kid... I just LOOK old ;-)

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

In article , Luhan Monat wrote: [.. zener in return ..]

True for small values of "very". Most op-amps have a PSRR that decreases with frequency. The neg rail PSRR is usually much worse than the plus rail. A capacitor across the Zener will help a lot.

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kensmith@rahul.net   forging knowledge

In article , Jim Thompson wrote: [...]

Is there an existing substrate pump? If so can you take some current from it?

Is anything at ground?

-1.5V give or take how much?

I suggest a Pelter device between the chip and the heat sink.

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kensmith@rahul.net   forging knowledge

I once bought a 16K RAM pack for the ZX81, and it used 4116 chips. These need +12V and -5V, as well as the usual +5V.

The ZX81 only had +9V unregulated, and +5V.

I found they wired the +9V to the +12V rail (ugh!), and used a 555 timer as an oscillator to drive a charge pump to make -5V.

I suspect they could have just used the CPU CLK (3.5 MHz) and a buffer gate (or a pair of transistors) to drive a charge pump, and thus use smaller caps.

Nice. I got to program a modern GenRad a few years back, it was fun. Until one of the 0V relays froze - there were 32 in parallel. Fixing it was fun though - I got the production staff to randomly call out numbers, and I pulled those relays out. Got it the 5th time.

Cheers Terry

In article , Jim Thompson wrote: [...]

Yes

Here's a couple of free ideas (and worth every penny)

If the drive to the P-MOSFET has a known duty cycle, can you get away with AC coupling the drive to it? This seriously decreases the number of parts that swing below ground.

In EEPROMs and FLASHes, they trap a hand full of electrons on a floating gate electrode placed above the channel of a MOSFET.

Now for a dumb question: Why not use an N-channel?

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kensmith@rahul.net   forging knowledge

Leakage when off. I'm dealing with pA.

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

Hmmm! How much power? My total power budget is < 100uA.

...Jim Thompson

-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |

| 1962 | I love to cook with wine. Sometimes I even put it in the food.

In article , Jim Thompson wrote: [....]

Bummer!

Use a MEMS relay

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kensmith@rahul.net   forging knowledge

reminds me of the RAM "upgrade" I gave my ZX81 as a boy. $200 later, it worked again - I didnt know about PTH....still I was about 12, a fairly good excuse. Mine was colour too - I didnt have a TV, but used a tabletop Videogame instead (very rough on neck). Colour was manually set, until I got a printer port and used that to set the background colour. The defender machine beside the ZX81 got more use though :) [oh, the joys of mum & dad owning a few thousand videogames]

Cheers Terry

They can be electrostatically actuated so the static power is zero.

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kensmith@rahul.net   forging knowledge