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.

 

[William P.N. Smith]

kellrobinson@billburg.com wrote:

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.

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?

 

William P.N. Smith wrote:

kellrobinson@billburg.com wrote:

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.

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?

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?

 

[Franc Zabkar]

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

William P.N. Smith wrote:
kellrobinson@billburg.com wrote:

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.

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?

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?

Why not use a single IC solution with built-in temperature
compensation, eg http://focus.ti.com/lit/ds/symlink/uc3906.pdf?

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
--
Please remove one 'i' from my address when replying by email.

 

Franc Zabkar wrote:

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

William P.N. Smith wrote:
kellrobinson@billburg.com wrote:

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.

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?

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?

Why not use a single IC solution with built-in temperature
compensation, eg http://focus.ti.com/lit/ds/symlink/uc3906.pdf?

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
--
Please remove one 'i' from my address when replying by email.

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.

 

[Franc Zabkar]

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

Franc Zabkar wrote:
On 5 Jan 2006 15:14:48 -0800, kellrobinson@billburg.com put finger to
keyboard and composed:

William P.N. Smith wrote:
kellrobinson@billburg.com wrote:

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.

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?

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?

Why not use a single IC solution with built-in temperature
compensation, eg http://focus.ti.com/lit/ds/symlink/uc3906.pdf?

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
--
Please remove one 'i' from my address when replying by email.

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.

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
--
Please remove one 'i' from my address when replying by email.