diode series

I'm looking for a component that has 12 or 15 silicon diodes in series, or an array with pinouts for diodes that I can connect in series. Low current application, a few milliamps. Might be able to work with led's, but the tempco on most led's is too low for the purposes of my project.

Reply to
kellrobinson
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Make up your mind! 8*) I take is this is last-year's project from

12/29 about an array of LEDs with a different approach? Why not tell us what you are trying to do, you might get some good ideas.

For instance, what voltage do you need on your reference, at what tolerance, and with what tempco?

Reply to
William P.N. Smith

I need a tempco of about -25 mV/deg C. I already built a prototype using diodes in series and don't like soldering lots of diodes. It exceeds the total number of components in the rest of the circuit, and consumes time. This is a voltage regulator with temperature compensation for charging 12 volt lead acid batteries, which call for temperature compensation between -18 and -33 mv/deg C, depending on the battery construction. The batteries in question undergo extreme temperature variations and have short lives if used on fixed voltage regulators. And no, it's not for a UPS.

I decided against taking a small voltage reference, like a diode or two, and scaling it up using a resistive voltage divider. I prefer not to deal with touchy pot adjustments. I use a series of about a dozen diodes or so to get the tempco right and then stick a zener in the series to bring the voltage up the rest of the way.

Now are you satisified?

Reply to
kellrobinson

On 5 Jan 2006 15:14:48 -0800, snipped-for-privacy@billburg.com put finger to keyboard and composed:

Why not use a single IC solution with built-in temperature compensation, eg

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The tempco of the internal 2.3V reference is -3.5mV/C which scales up to 13.8V and -21mV/C.

There are other switchmode solutions which would be more efficient.

- Franc Zabkar

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Reply to
Franc Zabkar

I didn't think going into a long explanation would help, and it looks like I was right. This is a voltage regulator on a vehicle. Not an offline battery charger. Switchmode is too complicated. There's a max of about 2.3 amps field current to regulate, and I use hysteresis to keep the main switching element from heating up. Very simple circuit.

Reply to
kellrobinson

On 8 Jan 2006 19:18:27 -0800, snipped-for-privacy@billburg.com put finger to keyboard and composed:

Years ago I built an alternator regulator using a Motorola MC3325. It has an on-chip string of diodes (including one zener) for setting the tempco, and it is linear. I don't know what is available today, but I believe ST Microelectronics has several single-chip solutions, both linear and switchmode. My old SGS Automotive Products databook lists the L9480VB which comes in a 3-pin TO220 package. You can't get any simpler than that. :-)

- Franc Zabkar

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Reply to
Franc Zabkar

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