Question about parts and Interfaces

James Long

I know this isn't the best place to post this.....but because I'm designing with the Propeller.....I figure it will work.

Do any of the people here, have a list of parts they normally use on thier surface mount designs. This is my first surface mount board....so I'm working hard on just finding parts. I'm looking for standard part numbers for Mouser,Digikey,Jameco.

I usually have a spreadsheet of parts that·I use....to keep the process organised.

I'm a solder junkie...so I don't think it will be hard to transition to surface mount.....if I can find the parts.

Also...what is the optimum interface for the Propeller for programming? (I want to ensure that I can interface with the chip after the board is finished)

Please understand ....I'm designing sight unseen. I don't not own a Propeller chip...but I know what I need.Most of my project is I2C and Serial communication. I have a few ADC items.....but these are actually quite easy.

I have the chips on my list...like the MAX1202(12bit ADC with 3.3v interface)·and the MAX3232E(Rs-232 communication interface 5v to 3v).

The things I need are capacitors, resistors, enhanced N channel Mosfets, Voltage regulators(3.3v, 5v, 6v)........and the like.

Thanks for the help,

James

Chris Savage

James,

·· We in Tech Support highly recommend prototyping your system before designing a PCB around a chip you don't own.· You could use a DIP-40 version of the chip for prototyping.· Take care.


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Chris Savage
Parallax Tech Support
csavage@parallax.com


Post Edited (Chris Savage (Parallax)) : 8/31/2006 5:13:14 PM GMT

Mike Green

Look at the design of the Propeller Demo Board and the PropStick for tested examples of USB and serial programming interfaces. Both schematics have been posted before. You can also use a USB to logic level converter like the USB2SER, Prop Clip, or Prop Plug if you don't want to include your own interface on the board.

Ditto on Chris's advice to prototype first on an easy to manipulate physical platform like either the Demo Board, Wulfden's Propeller Robot Controller, or the PropStick on a breadboard strip.

Phil Pilgrim (PhiPi)

Definitely get some Propeller mileage under your belt before laying out a PCB for it. But, that said, places like APCircuits (www.apcircuits.com) are so fast and cheap for proto boards, you can almost think of it as breadboarding. As to SMD components, if you're new to the game, stick with 0805s or larger for your passives — especially if you're hand soldering. Also, stay away from the leadless MLP-type packages, in favor of the leaded QFPs. And when laying out a board, be generous with pad sizes: it makes soldering that much easier.

After one too many tombstoned resistors, though, you'll want to move to solder paste and an oven. Use a paste with RMA flux. You have to clean it off afterwards with 99% isopropyl alcohol and a toothbrush, but it "takes" better than the no-clean types. I use a Panasonic infrared toaster oven with electronic time and temperature controls. The profiling has to be done by hand (2.5 min. at 285F, then 0.5-1.0 min. at 460F), but it works. At this point 0603s become realistic for passives, too. (I've never tried 0402s. The 0603s are about the limit of what I can see, as it is.)

With either method, make sure you have plenty of small caliber solder wick on hand. It can turn a globby mess into a work of art!

-Phil

James Long

Chris said...
·We in Tech Support highly recommend prototyping your system before designing a PCB around a chip you don't own.· You could use a DIP-40 version of the chip for prototyping.· Take care.

Chris,

I appreciate your insight into this, but I have a project that would benefit from a smaller chip. Size is a problem here. I hate to be a cheapskate, but I really can't afford to build two systems (one prototype and one production).

Mike said...
Look at the design of the Propeller Demo Board and the PropStick for tested examples of USB and serial programming interfaces. Both schematics have been posted before. You can also use a USB to logic level converter like the USB2SER, Prop Clip, or Prop Plug if you don't want to include your own interface on the board.

Ditto on Chris's advice to prototype first on an easy to manipulate physical platform like either the Demo Board, Wulfden's Propeller Robot Controller, or the PropStick on a breadboard strip.

That is a good idea.....that would make the schematics easier to draw and the interfaces would be known to work.

Phil said...
Definitely get some Propeller mileage under your belt before laying out a PCB for it. But, that said, places like APCircuits (www.apcircuits.com) are so fast and cheap for proto boards, you can almost think of it as breadboarding. As to SMD components, if you're new to the game, stick with 0805s or larger for your passives — especially if you're hand soldering. Also, stay away from the leadless MLP-type packages, in favor of the leaded QFPs. And when laying out a board, be generous with pad sizes: it makes soldering that much easier.

After one too many tombstoned resistors, though, you'll want to move to solder paste and an oven. Use a paste with RMA flux. You have to clean it off afterwards with 99% isopropyl alcohol and a toothbrush, but it "takes" better than the no-clean types. I use a Panasonic infrared toaster oven with electronic time and temperature controls. The profiling has to be done by hand (2.5 min. at 285F, then 0.5-1.0 min. at 460F), but it works. At this point 0603s become realistic for passives, too. (I've never tried 0402s. The 0603s are about the limit of what I can see, as it is.)

With either method, make sure you have plenty of small caliber solder wick on hand. It can turn a globby mess into a work of art!

Phil,

I don't have many·items on the board, a few resistors, an op-amp, some capacitors, some max chips like I previously stated,·some voltage regulators, and some headers. The board is not really complicated. I just want to·insure the applied components will work correctly.

Would you consider·baking a board if I sent it to you with the components? I would pay for the service ofcouse.


To all.......could you passively approve a design schematic if posted here? I was planning on getting opinions of my final schematic before having it etched/routed.

Just an Idea......

James·

Chris Savage

James said...(trimmed)

Chris said...
·We in Tech Support highly recommend prototyping your system before designing a PCB around a chip you don't own.· You could use a DIP-40 version of the chip for prototyping.· Take care.

Chris,
I appreciate your insight into this, but I have a project that would benefit from a smaller chip. Size is a problem here. I hate to be a cheapskate, but I really can't afford to build two systems (one prototype and one production).

James,

·· The cost of a design error in a production PCB·could be a lot more.· Just some advice.· Take care.

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Chris Savage
Parallax Tech Support
csavage@parallax.com

James Long

Chris said...
The cost of a design error in a production PCB·could be a lot more.· Just some advice.· Take care.

Chris,

Thanks.....I do appreciate your view.....I know you deal with this kind of thing everyday, and appreciate the support you give on the forum and otherwise.

I just will have to make sure not to make a mistake .


James

Phil Pilgrim (PhiPi)

James,

If you go from straight from "brain to PCB", you definitely need to do a cheap (no soldermask or silkscreen) proto board first!!! There's just no getting around the high probability of errors on the first go 'round, regardless of how few parts there are. Then you need to take one plain and one assembled proto board to a production assembly house for a quote and a critique. And believe me, they will critique it. They'll say things like, "You used the manufacturer's suggested pad sizes? No good. Make 'em bigger.", and "Where are your fiducials?" It's a rite of passage that's not to be missed! But a good assembly engineer will save you all sorts of grief down the road. So it's well worth the time to go visit. But if they don't spend the time with you, go somewhere else. They're not worth dealing with.

As to populating and baking your board for you, I'm afraid I'll have to decline. Sorry. It's all I have the patience and eyesight for to do my own. But there are plenty of businesses out there who specialize in assembling one-off protos. Type prototype pcb assembly into Google, and you'll find a ton of them. Add the name of your state to the search, and you'll find some close to home.

You're embarking on an adventure, and there will be frustrations. But don't get discouraged. You will prevail in the end.

Good luck!
Phil

James Long

Phil said...
If you go from straight from "brain to PCB", you definitely need to do a cheap (no soldermask or silkscreen) proto board first!!! There's just no getting around the high probability of errors on the first go 'round, regardless of how few parts there are. Then you need to take one plain and one assembled proto board to a production assembly house for a quote and a critique. And believe me, they will critique it. They'll say things like, "You used the manufacturer's suggested pad sizes? No good. Make 'em bigger.", and "Where are your fiducials?" It's a rite of passage that's not to be missed! But a good assembly engineer will save you all sorts of grief down the road. So it's well worth the time to go visit. But if they don't spend the time with you, go somewhere else. They're not worth dealing with.

As to populating and baking your board for you, I'm afraid I'll have to decline. Sorry. It's all I have the patience and eyesight for to do my own. But there are plenty of businesses out there who specialize in assembling one-off protos. Type prototype pcb assembly into Google, and you'll find a ton of them. Add the name of your state to the search, and you'll find some close to home.

You're embarking on an adventure, and there will be frustrations. But don't get discouraged. You will prevail in the end.

Phil,

That is a good idea.....plus I doubt that I ever mass produce this design.

What are fiducials???·· I have a lot to learn.

I thought I would ask......hey I tried right?!!·· I will populate it myself. I'm just not sure what components are the right size......I really need a chart of part differences....there seems to be millions of variations on the same theme.

But on that same note.......I will still submit my drawings to be critiqued...builds character.

I'm not an electronics level guy by trade....I have basically learned all of this on my own over the last 15 years. I'm just taking the next step into the abyss.

Thanks for all the support and advice.

You guys are really great,

James

Post Edited (James) : 9/1/2006 3:26:09 AM GMT

Phil Pilgrim (PhiPi)

James,

Fiducials are reference pads on the board that the automated pick-and-place machinery uses for alignment. You can read about them here: www.tkb-4u.com/articles/other/fiducial/fiducial.php

-Phil

James Long

Phil said...
Fiducials are reference pads on the board that the automated pick-and-place machinery uses for alignment. You can read about them here: www.tkb-4u.com/articles/other/fiducial/fiducial.php

That makes sense......I'm an automation technician by trade....so that explains it perfectly..no need to read.

I learned a new term.

James

Phil Pilgrim (PhiPi)

James,

Unless you somehow already know what size and shape to make the fiducials, how much soldermask clearance they require, and where to put them, you might want to read the article. The same road that's paved with good intentions is also littered with bad assumptions.

Here are some other design rules to consider. Numbers 1 through 4 are fabricator-dependent, so you should check with your desired fab house for more precise recommendations.

1. Make sure trace widths and separations at least 0.008".
2. Silkscreen lines should be at least 0.005" wide.
3. Add about 0.006" overall (0.003" radius) to pads for soldermask.
4. If pads on a fine-pitch part are closer than X, use a siingle soldermask cutout for the whole row of pads to prevent a fine web of mask between pads which could separate from the board. (X is fabricator-dependent.)
5. Pastemask is usually the same size as the pad.
6. Keep at least 0.030" between parts.

In any event, most fab houses will publish their design rules on their website. Assembly houses will make additional recommendations about pad sizes for different kinds of parts. Their concerns mostly deal with making sure there's enough pad around the part for a visible solder fillet. This makes the connection not only more reliable but also easier to inspect. For leaded parts like SOICs and QFPs, they may recommend different clearances for "heel" (behind the bend of the lead) and "toe" (off the tip of the lead) fillets. Most will pooh-pooh the part manufacturers' recommendations for pad layout as being too tight. (Chip's Propeller QFP layout, by contrast, accommodates plenty of clearance and shouldn't meet any objections.) In any event, the sooner you get your board assembler involved in the design process, the less reengineering you'll have to do.

-Phil

Tracy Allen

If you are using a CAD package for circuit board layout, and it produces a Gerber file, you can have a design check run online from a service like http://www.freedfm.com. It will catch things like pads too close, insufficient solder mask relief and so on. The one I cited is a tool for one fabricator (Advanced Printed Circuits) in Colorado, but these requirements are fairly consistent across the industry. If you are going to produce multiple copies of something, it is a good idea to stick with one good fabricator and one assembler, (provided they do a good job at a fair price!) because you learn the particular ropes of how they do business and how they want the parts and instructions. But James, it sounds like you are not going into production with this. It is still possible to run the design checks.

I'd want to have a working prototyping board too, in addition to the custom made invention board. When you have a new circuit board, there are so many possible causes for it not working. If you purchase something like the demo board or a propstick, you can be assured that you know how to operate the IDE, and that your computer is set up properly to make the connection to the Prop, and that you know how to download a program that will blink an led. When you have only your custom circuit board, all of those things are in the line of possible trouble, and the troubleshooting task can be daunting. That is particularly true if you are hand soldering your first surface mount board. If you have something like a demo board, you can try out the individual circuits of you project one at a time and also the internal Prop objects in an modular fashion, so when you move it to your own board the possible causes of failure are narrowed down to a managable level.

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Tracy Allen
www.emesystems.com

James Long

Phil said...
Their concerns mostly deal with making sure there's enough pad around the part for a visible solder fillet. This makes the connection not only more reliable but also easier to inspect. For leaded parts like SOICs and QFPs, they may recommend different clearances for "heel" (behind the bend of the lead) and "toe" (off the tip of the lead) fillets. Most will pooh-pooh the part manufacturers' recommendations for pad layout as being too tight. (Chip's Propeller QFP layout, by contrast, accommodates plenty of clearance and shouldn't meet any objections.)

This is very interesting.....that would mean ....that I would have to totally redesign my board after designing it once. What a pain.

Tracy said...
If you are using a CAD package for circuit board layout, and it produces a Gerber file, you can have a design check run online from a service like http://www.freedfm.com. It will catch things like pads too close, insufficient solder mask relief and so on. The one I cited is a tool for one fabricator (Advanced Printed Circuits) in Colorado, but these requirements are fairly consistent across the industry. If you are going to produce multiple copies of something, it is a good idea to stick with one good fabricator and one assembler, (provided they do a good job at a fair price!) because you learn the particular ropes of how they do business and how they want the parts and instructions. But James, it sounds like you are not going into production with this. It is still possible to run the design checks.

I'd want to have a working prototyping board too, in addition to the custom made invention board. When you have a new circuit board, there are so many possible causes for it not working. If you purchase something like the demo board or a propstick, you can be assured that you know how to operate the IDE, and that your computer is set up properly to make the connection to the Prop, and that you know how to download a program that will blink an led. When you have only your custom circuit board, all of those things are in the line of possible trouble, and the troubleshooting task can be daunting. That is particularly true if you are hand soldering your first surface mount board. If you have something like a demo board, you can try out the individual circuits of you project one at a time and also the internal Prop objects in an modular fashion, so when you move it to your own board the possible causes of failure are narrowed down to a managable level.

I'm using Eagle...so I do have the required files.

Thanks for the encouragement.....I'm sure I will need it.

James

Phil Pilgrim (PhiPi)

James said...
This is very interesting.....that would mean ....that I would have to totally redesign my board after designing it once. What a pain.

That's what happened to me on my first SMT board. But it was a small one, so the pain was minimal. I guess it's a good argument for keeping your first project a simple one. Also keep in mind that the same considerations that make a production board easy to assemble and inspect apply in spades to a hand-soldered proto board. You'll come to appreciate the extra pad perimeters and wide parts placement when you're hovering over the board with a part in tweezers or nudging one into place with a spudger.

Tracy's design rule checking recommendation is spot on. Some PCB CAD programs have this facility built-in. I use CADINT, which does. I'm not sure about Eagle, though. If it does, use it early, and use it often during the layout process. It will help keep you from painting yourself into a too-tight corner.

-Phil

James Long

To change the topic a little....because I started the thread....

I have a small problem that I can't seem to figure out.

I have three voltage regulators on my board. Of which all have three pins.....but Eagle places three pins and one large pad for the main body of the regulator....I hate to be stupid.....what is the large pad for??

I don't get it.....its things like this that really catch me off guard. Is the large pad connected to a +/- supply??

All the documentation of the part(s) do not reference this. Is this just for mounting??

Things like this are the reason I was reluctant to switch my building method. But·times change and we have to comply with them.

Just trying to learn about the new components/methods.

James

Harley

James said...


I have a small problem that I can't seem to figure out.

I have three voltage regulators on my board. Of which all have three pins.....but Eagle places three pins and one large pad for the main body of the regulator....I hate to be stupid.....what is the large pad for??

I don't get it.....its things like this that really catch me off guard. Is the large pad connected to a +/- supply??

All the documentation of the part(s) do not reference this. Is this just for mounting??

Things like this are the reason I was reluctant to switch my building method. But·times change and we have to comply with them.

Just trying to learn about the new components/methods.

James

Since you didn't show us what you are seeing, I'm guessing it might be a pad to screw down a TO-220 regulator parallel to the board. For some uses a heat sink is installed under the regulator; for light loads it probably isn't needed.

If you mount vertically, then the 'mount' would be 'off board', if required.

Do you have a document for the part in question? Is the dimensions from leads to the 'large pad' appear correct, accounting for lead bend radius?

Voltage drop from input to output * load current is a quick calc to determine if the regulator is running warm (or very HOT ).

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Harley Shanko
h.a.s. designn

James Long

Harley said...
Since you didn't show us what you are seeing, I'm guessing it might be a pad to screw down a TO-220 regulator parallel to the board. For some uses a heat sink is installed under the regulator; for light loads it probably isn't needed.

If you mount vertically, then the 'mount' would be 'off board', if required.

Do you have a document for the part in question? Is the dimensions from leads to the 'large pad' appear correct, accounting for lead bend radius?

Voltage drop from input to output * load current is a quick calc to determine if the regulator is running warm (or very HOT ).

Well that is the problem....this is not the typical through the hole mounting scenario.....this is surface mount....and this is where the problem comes in.

I have enclosed a picture· from another software that shows the pads. It also gives the part number (provided by me), so you can try and find out what the large pad is for.

I would assume (oh....that dreaded word) it is for a heat sink type solder attachment.....but I'm only guessing.

Let me know what you think guys.

James

Post Edited (James) : 9/2/2006 12:49:12 PM GMT

Phil Pilgrim (PhiPi)

James,

I looked at the Micrel datasheet for the MIC29300. In it you will find the following info:

1. The -BU suffix means it's in a TO-263 package.
2. The tab is grounded.
3. Pin 1 is input; 2 is ground; 3 is output.

The tab is a heatspreader and gets soldered to that large pad, which you correctly surmised is for heatsinking. (I'm not sure how much of that pad gets pasted, though. But there's probably a paste layer associated with the part in your CAD program that will show you.) If the device will dissipate a lot of heat, you will want to include the pad in your groundplane to make the most thermal mass available to it. If your groundplane is on the opposite side of the board, you can use an array of plated through-holes as a thermal conduit to reach it. Just don't put the holes in your pasted area, else the solder will get sucked into them.

-Phil

James Long

Phil said...
James,

I looked at the Micrel datasheet for the MIC29300. In it you will find the following info:

1. The -BU suffix means it's in a TO-263 package.
2. The tab is grounded.
3. Pin 1 is input; 2 is ground; 3 is output.

The tab is a heatspreader and gets soldered to that large pad, which you correctly surmised is for heatsinking. (I'm not sure how much of that pad gets pasted, though. But there's probably a paste layer associated with the part in your CAD program that will show you.) If the device will dissipate a lot of heat, you will want to include the pad in your groundplane to make the most thermal mass available to it. If your groundplane is on the opposite side of the board, you can use an array of plated through-holes as a thermal conduit to reach it. Just don't put the holes in your pasted area, else the solder will get sucked into them.

-Phil

Now see.....that is the kind of answer I like.........too bad I don't have a full list of parts that I'm confused about.

Phil.....I found all the electrical connections ( I had the datasheet)......that was self explanitory....I just didn't know about the large pad surface.

Thanks for the answer,

James

Harley

James said...
Now see.....that is the kind of answer I like.........too bad I don't have a full list of parts that I'm confused about.


Phil.....I found all the electrical connections ( I had the datasheet)......that was self explanitory....I just didn't know about the large pad surface.

I'd say it is time to go through that 'full list of parts' and undo any confusion PRIOR to going to pcb layout. Need to know: outside dimensions for parts spacing, pad/hole sizes for connections or mounting schemes (tabs, screw holes, etc.), solder paste area dimensions (for both paste and solder mask layers), just the beginning of a list of layout details to consider.

James also said...
Well that is the problem....this is not the typical through the hole mounting scenario.....this is surface mount....and this is where the problem comes in.

I don't have the regulator data sheet, but if one read it carefully it probably mentions about the thermal tab, its function, and possibly thermal considerations for proper use.

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Harley Shanko
h.a.s. designn

James Long

Phil said...
I looked at the Micrel datasheet for the MIC29300. In it you will find the following info:

Phil,

I have a datasheet, but it is not specifically for the MIC29300......it contains about five different packages. Maybe that was my main problem.

Where did you get the specific datasheet for that one regulator.

Harley said...
I'd say it is time to go through that 'full list of parts' and undo any confusion PRIOR to going to pcb layout. Need to know: outside dimensions for parts spacing, pad/hole sizes for connections or mounting schemes (tabs, screw holes, etc.), solder paste area dimensions (for both paste and solder mask layers), just the beginning of a list of layout details to consider.

Yea...that is a great idea.....I will have to make a list·of areas with·confusion. This could be the surface mount board design 101!! (Sticky)

This design is not finished....so I can post my progress as I go.....then you guys can say, "Whoa!! wait that won't work!!"

I didn't find anything about the thermal tab being grounded or it getting soldered....so that is the reason for me asking.

I will continue and post pics/files as I go.

What method would be the best?

James

Phil Pilgrim (PhiPi)

James,

Yours sounds like the datasheet I looked at: TO-220's, TO-263-3's, and TO-263-5's. This is common for many semiconductor products: one datasheet for a family of similar parts. You have to read the fine print to get the specifics for a particular device.

-Phil

James Long

Phil said...
Yours sounds like the datasheet I looked at: TO-220's, TO-263-3's, and TO-263-5's. This is common for many semiconductor products: one datasheet for a family of similar parts. You have to read the fine print to get the specifics for a particular device.

Oh my.....I will admit ...you are absolutely correct. I have read that datasheet atleast 10 times.....and all the time I was overlooking the part that states,"On all devices, the Tab is gounded."

Wow......that sucks....now I feel real stupid. It was in a place that·I just didn't notice it.

On to the next stupid question......I'll have to think of it first though.

James

Harley

James said...
Yea...that is a great idea.....I will have to make a list·of areas with·confusion. This could be the surface mount board design 101!! (Sticky)

This design is not finished....so I can post my progress as I go.....then you guys can say, "Whoa!! wait that won't work!!"

I didn't find anything about the thermal tab being grounded or it getting soldered....so that is the reason for me asking.

I will continue and post pics/files as I go.

What method would be the best?

I googled for the MIC29300, and sure enough it doesn't indicate what the 'tab' is. Only if you've worked with such before might one know. However, there is mentioned on pg 1, under Pin Configuration in the 'box' is mention of pinout notes, with "On all devices, the Tab is grounded". On a quick pass through the 15 page data sheet did I find mention of dealing with the 'tab', like having it soldered to a good thermal ground, and power ground.

Some of us on the forum might be almost 'older than dirt', but we can help when we have enough info to know what your needs are. Hopefully, any critiques won't be taken personally; just trying to steer one towards a better solution. (I've done over 100 pc boards, originals and revisions. Some tiny, one about 15 x 18", many through-hole and a number also with SMD parts, many 4-layer, some 6-layer, some with hi-freq considerations -- MECL with 500 MHz clock for part of one design, several with matched length transmission lines, etc.) So some details become obvious when 'eyeballed', like a regulator 'tab'.

For What method is best question:
...Well, many times just a textual description is sufficient, other times some drawing or graphic is better. If you have a digital camera, a '.jpg' shot can be very useful and quick. If you are dealing with a pcb layout, hmmm, maybe a screen dump of the area in question can be sufficient, unless the layout program can output a picture in a useful format.

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Harley Shanko
h.a.s. designn

James Long

Harley said...
I googled for the MIC29300, and sure enough it doesn't indicate what the 'tab' is. Only if you've worked with such before might one know. However, there is mentioned on pg 1, under Pin Configuration in the 'box' is mention of pinout notes, with "On all devices, the Tab is grounded". On a quick pass through the 15 page data sheet did I find mention of dealing with the 'tab', like having it soldered to a good thermal ground, and power ground.

Some of us on the forum might be almost 'older than dirt', but we can help when we have enough info to know what your needs are. Hopefully, any critiques won't be taken personally; just trying to steer one towards a better solution. (I've done over 100 pc boards, originals and revisions. Some tiny, one about 15 x 18", many through-hole and a number also with SMD parts, many 4-layer, some 6-layer, some with hi-freq considerations -- MECL with 500 MHz clock for part of one design, several with matched length transmission lines, etc.) So some details become obvious when 'eyeballed', like a regulator 'tab'.

For What method is best question:
...Well, many times just a textual description is sufficient, other times some drawing or graphic is better. If you have a digital camera, a '.jpg' shot can be very useful and quick. If you are dealing with a pcb layout, hmmm, maybe a screen dump of the area in question can be sufficient, unless the layout program can output a picture in a useful format.

Hey.....I'm not that young either....I'm not a spring chicken.....

We will keep up the project and all can learn what I'm learning.

I rarely take things personally. Part of learning is being humble enough to know "No one knows everything!".

I may do things that most think are risky....but I do listen to the advice given.

I'm learning a lot of things at once.....so it is a lot to take in.

James


Post Edited (James) : 9/3/2006 1:59:02 AM GMT

Phil Pilgrim (PhiPi)

James,

Don't feel bad: I read it over at least that many times before I found the part describing the tab connection. The only difference is that I've been through this wringer enough times (but still approaching the age of dirt) that I knew it had to be there ... somewhere!

But it's always worth double-checking these things. On the LM317, for example, the tab is connected to Vout. (Okay, bad example, since the '317 has no ground connection. But still...)

-Phil

James Long

Phil said...
Don't feel bad: I read it over at least that many times before I found the part describing the tab connection. The only difference is that I've been through this wringer enough times (but still approaching the age of dirt) that I knew it had to be there ... somewhere!

But it's always worth double-checking these things. On the LM317, for example, the tab is connected to Vout. (Okay, bad example, since the '317 has no ground connection. But still...)

I was actually starting to think....I had to know the "surface mount secret handshake" to find out.

I know that most datasheets contain the needed information....but it was eluding me. That pesky bit of information. Like that specific·bit you are looking for in your program that makes the keyboard bloody. (From the forehead)

Its great to have a place online to learn things like this, and have people to help.

I'm really excited about my project......as long as I can hold out to see it done.

James

James Long

Ok....just to give a update.....I did it....I broke down and ordered the Prop demo board....I hated doing it....but it will give me some program time while I finish the design of my board and have you guys tear it apart.

Thanks for all the information so far.

I hate to say it...but at this moment, I'm overwhelmed (sp?) with what I have to do. This project has escalated to a point of massive porportions....I hope I'm up to this task.

I'm sure I will have a huge amounts of questions to get this project finished.

James

James Long

Ok....so now I have my demo board on the way....I've been working on my design of the proto board....but I came across a problem....does anyone have a library for Maxim that hass more of their chips in it (for Eagle)?

What about pressure sensors from motorola????

I don't want to have to draw them ....I just started using Eagle.....and don't care to learn that yet.



James L