TQFP handling while developing

It should be possible to solder the TQFP package into the application board and develop on that board. Provided you don't blow the DSPIC up, you should not need to remove it for debugging or programming - it's FLASH

-Andrew

What is the problem in creating an application specific board with everything on that is required for the project ? I do at least a board per project. Debugging is done on the board with an in circuit programmer. Those flash devices do at least 1000 cycles, usually sufficient to solve the problem.

Rene

Rene Tschaggelar schrieb:

The problem is, that you do not know before what hardware you need for a project, even in analog-applications. Software and hardware are developed together. You have not only to change the software, but also the hardware. And sometimes you need more than one controller. You cannot use a new board for maybe every 20 versions, because you cannot produce TQFD boards yourself. You have to give it away. And only one PCB is very expensiv and needs much time. If you could produce the PCB yourself, you make some changes in the layout and get a new one in half an hour.

Further controllers can be damaged, when you have a wild mess of soldered components. Especiallly audio-design and picoampere/microvolt measurings and applications with switched high voltage/currents are very messed, because her special demands of astral routing.

Because all that I have to solder the TQFP-processor on a special ilittle board, which can be inserted in the application developement board.

Further there is another problem: If you have finished developing with the adapted TQFP Controllers, you have to route the PCB new for the not adapted series version. And then things change. The audio or the measuring is wrong now, because disturbed by the controller. Or the application disturbes the processor now and it crashes.

And what is about emulation, when the processor is soldered into the board?

With socketable controllers like PLCC things were much easier. You could socket it and change it, when damaged. You could produce the developement versions of PCB yourself. Emulation is no problem: Plug the emulator into the socket of the controller. And the last developement version could without problems be the series version. And if you get problems to leave out the socket in the series version, you let him be,

Even for DS you need a controller, which has the same format in the development and the series version. And for this purpose PLCC was a good solution. It is the skimpiest format, that is reliable socketable. But of all things the DS!!-PIC is not available in this package. Maybe this shows, that mirochip is new in the (digital-)analog segment and is not familiar with its problems.

Vendors (initially) offer TQFP/SMD only, because that is where the volume business is.

It can, and does, change : examples

- Cygnal offer selected DIP packages of their MLF production devices

- Philips original LPC932 family did not include PLCC package, now, they do.

- IIRC, Atmels first data on the AT89C51ED2 also excluded PDIP, but now this is included.

So, mention it to Microchip.

If it is a 'show stopper', choose another uC...

-jg

Thank you, Paul for your long answer.

First I want to say, that my English is not very good. I do not know, whether I understood everything correctly. And do not know, whether I say everything that way, I want it to say. Sorry for this.

"Paul E. Bennett" schrieb:

This is a problem. I am the only designer in our company. The possibilities are a bit poor. :-( I have to solve every problem without companion and without assistance.

What is a naff project contol? Or better: What makes a project control the opposite of naff?

Could you explain that with other words ... my limited English. Sometimes I think, a good equipment makes your thoughts poor. I do not really know, which side is better to switch charitable mode on or off. ;-) But the die of PLCC is too hard. Some effects maybe compensated, but others not.

You are speaking from the little PCBs with the controller on it? Please, tell me more about "impedance controlled padding".

The analog section is devided from the digital by both grounds, which goes closed to the controller as possible. The backside (two layers) of the pcb is filled with ground - digital and analog devided to their sections.

Very good!!

Isn't it capacity? Please, tell me more.

I think I do it. Maybe there are some points, which I do not know.I use two or more grounds. Every section is screened by its own ground. Critical signals are double screened with its own signal, hardened by an amp and then with its ground. Astral wiring as most as possible.. Very critical points (high impedance) are devided by gaps in the PCB or sometimes wired in the air. In extreme situatuations they are sealed from the humidity. I use screen-sheets. I always use kelvin-design for critical measurements. I decouple wires with high and low current. The thermo effect of a soldering joint is annihilated by an inverse one, if disturbing. I take care of the route of every lead. I decouple switched high-voltage leads by resistances near to the switches, to avoid broadcast. This all for PCB route and real wire route. I hope I did not forget anything. Anything more to do?

But there is the mechanical process equipment, which is not always asked me. And sometimes the design of the electronic is made by optical aspects. They do not want the electronic to "get cluttered" to different places of the equipment, which would be useful for good decoupling. And sometimes the mechanical eqipment lets you not do, what would be good to avoid crosstalk and pickup. Although this, you have to provide a working design. And that could make problems when changing a working prototype layout because TQFP. But it helps, what you said above.

Still unanswered

They said, that I could program the controllers in-curcuit. I know that. This helps only for the software, but not for the hardware.

Maybe, I should calm down But that does not change this fact: The die of PLCC makes problems for analog-developement not easier. And I am quite safe, that this bothers not only me.

Jim Granville schrieb:

To the rehabilitation of Microchip I must say, that they offer DIP-dsPICs. But this is only possible until 40 leads. The PLCC would be the better solution, because it is smaller and all the same reliable contactable. And it has got more leads.

Careful design ...

I never used an emulator. They were to expensive to start with and meanwhile I have debugging techniques that are sufficient.

Rene