1 Amp DC/DC Converter Chip?

[bcjames]

I want to build a 5 Volt power suppply to run my PDA in my
glider from the 12 volt battery. Sometimes I use a 14 volt
battery too, so it needs some input voltage range. I'm
looking for suggestions and a DigiKey part number for a
suitable 1 amp DC/DC integrated power supply chip.

I'd like:
at least 80% efficient
no radio noise
Vin of 10.5 to 16.5 volts
Vout 5 volts
1 amp
low cost

I've looked at the LM2825 and the LTC1174-5, but I'd like to
hear from anyone who's done this.

Thanks

[Tim Ward]

"bcjames" > wrote in message
...
> I want to build a 5 Volt power suppply to run my PDA in my
> glider from the 12 volt battery. Sometimes I use a 14 volt
> battery too, so it needs some input voltage range. I'm
> looking for suggestions and a DigiKey part number for a
> suitable 1 amp DC/DC integrated power supply chip.
>
> I'd like:
> at least 80% efficient
> no radio noise
> Vin of 10.5 to 16.5 volts
> Vout 5 volts
> 1 amp
> low cost
>
> I've looked at the LM2825 and the LTC1174-5, but I'd like to
> hear from anyone who's done this.
>
> Thanks


Well, good luck. Anything that is 80% efficient and low cost is going to
have some RF noise.
You might look on the National Semiconductor website. They have an online
design tool using their parts -- it gives you a circuit and a parts list.
For some additional cost, they'll ship you a PC board and the parts.

Tim Ward

[Iwo Mergler]

bcjames wrote:
> I want to build a 5 Volt power suppply to run my PDA in my
> glider from the 12 volt battery. Sometimes I use a 14 volt
> battery too, so it needs some input voltage range. I'm
> looking for suggestions and a DigiKey part number for a
> suitable 1 amp DC/DC integrated power supply chip.
>
> I'd like:
> at least 80% efficient
> no radio noise
> Vin of 10.5 to 16.5 volts
> Vout 5 volts
> 1 amp
> low cost
>
> I've looked at the LM2825 and the LTC1174-5, but I'd like to
> hear from anyone who's done this.
>
> Thanks
>
>

Check out Maxim, they tend to be very helpful
with samples. They also have parts with ring
damping circuitry which would help with the
radiated noise.

Another option is to download LTSpice
( http://www.linear.com/software/ ).
That software has a switcher designer
wizzard, you enter your parameters and
it spits out a circuit you can simulate.

Depending on your experience and amount of
effort you want to spend, it may be worthwile
to look into DC-DC converter modules.

Kind regards,

Iwo

[Jim Vincent]

Use a switch mode or buck regulator. Input range at least from 10-14 volts, go
with fixed output 5V.

I build one last year using a chip and a few passives thrown on a circuit
board. Pretty easy. I'd have to dig in the ship, though, to get the Part
Number. Just Google away...many good options from Maxim, etc. Explore Digikey
and others to get all the parts together. Radio Shack won't suffice. Contact
me directly for more help.

Alternatively, you might find an evaluation kit or an off-the-shell solution
like from http://www.soarmn.com/cumulus/

I chose to build my own because I learned a new gizmo! Plus, many years ago I
learned which end of a soldering iron to hold...took a few tries ;-)

Jim Vincent
N483SZ

[tango4]

http://www.internationalsoaring.org/78hc205.pdf

Needs some attention to good ground circuit, input filter and screening but
work very well - 10 - 30 volt input, 2 amp output.

Ian

[[email protected]]

bcjames > wrote in message >...
> I want to build a 5 Volt power suppply to run my PDA in my
> glider from the 12 volt battery. Sometimes I use a 14 volt
> battery too, so it needs some input voltage range. I'm
> looking for suggestions and a DigiKey part number for a
> suitable 1 amp DC/DC integrated power supply chip.
>
> I'd like:
> at least 80% efficient
> no radio noise
> Vin of 10.5 to 16.5 volts
> Vout 5 volts
> 1 amp
> low cost
>
> I've looked at the LM2825 and the LTC1174-5, but I'd like to
> hear from anyone who's done this.
>
> Thanks

Hi;

Have a look at the TI integrated switching regulators. This part and
a couple of capacitors will be all you need.

http://dkc3.digikey.com/PDF/T043/1317.pdf

Here is an app note for use in a car:

http://focus.ti.com/lit/an/slta010a/slta010a.pdf

These are nice overload protected parts and will get you going pretty
quickly.

Scott

[Glen Kelley]

Here's an easy approach. Go to
http://www.national.com/store/view_item/index.html?nsid=LM2675-5.0EVAL

order the National Semiconductor LM2675 demo board ($8!). All you have to
do is wire input voltage and output voltage (5v, 1A) to the board. It is @
90% efficient.

I have been using this converter for my Ipaq this season and it works great.
No RFI that I can tell.

Good luck.
"bcjames" > wrote in message
...
>I want to build a 5 Volt power suppply to run my PDA in my
> glider from the 12 volt battery. Sometimes I use a 14 volt
> battery too, so it needs some input voltage range. I'm
> looking for suggestions and a DigiKey part number for a
> suitable 1 amp DC/DC integrated power supply chip.
>
> I'd like:
> at least 80% efficient
> no radio noise
> Vin of 10.5 to 16.5 volts
> Vout 5 volts
> 1 amp
> low cost
>
> I've looked at the LM2825 and the LTC1174-5, but I'd like to
> hear from anyone who's done this.
>
> Thanks
>
>

[George Hamilton]

Radio Shack sells numerous solid state voltage regulators for pennies.
Easy to use and wire for your requirements.

GHamilton
N7409J

[COLIN LAMB]

The Radio Shack regulators are very inefficient. If you need 5 volts and
run 13 volts input, the 8 volt drop represents total loss. Total power loss
is determined by multiplying the 8 volt drop by the current draw. When
battery power is precious, it is better to use a converter chip to actually
convert the 13 volts to 5 volts - at over 80% efficiency.

The few extra dollars paid to purchase a converter rather than a voltage
dropping regulator is paid back over the life of the equipment.

Colin N12US


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[Eric Greenwell]

COLIN LAMB wrote:
> The Radio Shack regulators are very inefficient. If you need 5 volts and
> run 13 volts input, the 8 volt drop represents total loss. Total power loss
> is determined by multiplying the 8 volt drop by the current draw. When
> battery power is precious, it is better to use a converter chip to actually
> convert the 13 volts to 5 volts - at over 80% efficiency.
>
> The few extra dollars paid to purchase a converter rather than a voltage
> dropping regulator is paid back over the life of the equipment.
>
> Colin N12US
>
>
> ---
> Outgoing mail is certified Virus Free.
> Checked by AVG anti-virus system (http://www.grisoft.com).
> Version: 6.0.742 / Virus Database: 495 - Release Date: 8/19/04

To elaborate on what Colin said: to provide 700 milliamp charging
current to the Ipaq, your 12 volt battery must supply:

* Radio Shack voltage regulator at 12 volts: 700 milliamps
at 14 volts: 700 milliamps

* 80% efficient switching regulator at 12 volts: 360 milliamps
at 14 volts: 310 milliamps

My 3835 Ipaq can draw over 900 milliamps while charging and running a
program; my 2215 can draw abut 700 milliamps. It does drop off by about
50% when fully charged.

--
Change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

[Jim Vincent]

>nyone know how to
>tell the IPAQ not to charge its internal battery off my
>glider battery?

Todd, I think that depends on which pin you have the power going to. On my
Pocket PC and on my Sony Clie, one pin just powers the electronics, another
powers the electronics and charges the battery. Your pinout schematic should
have that info. Another option is to fully charge the battery the night
before. Keep in mind the current draw changes accordingly to the demands of
charging.

Jim Vincent
N483SZ

[Tom Seim]

bcjames > wrote in message >...
> I want to build a 5 Volt power suppply to run my PDA in my
> glider from the 12 volt battery. Sometimes I use a 14 volt
> battery too, so it needs some input voltage range. I'm
> looking for suggestions and a DigiKey part number for a
> suitable 1 amp DC/DC integrated power supply chip.
>
> I'd like:
> at least 80% efficient
> no radio noise
> Vin of 10.5 to 16.5 volts
> Vout 5 volts
> 1 amp
> low cost
>
> I've looked at the LM2825 and the LTC1174-5, but I'd like to
> hear from anyone who's done this.
>
> Thanks

Digi-Key does carry dc-dc modules that are self contained except for
some external capacitance. They are quite low noise; I have used them.
Designing a converter from components is best left to the pros (I am a
pro and I avoid it).

Tom