13V Supply for PIC Programmer

[CMOS]

7812 13v

Out of many PIC programmers designs available I've found that in some designs 13V Vpp is derived using series combination of 7805 and 7808
while some designs use LM317.
Which one is better and why?

 

[davorin]

5v to 13v dc dc charge pump

The 7805/7808 solutions supplies also the 5V besides the 5V (o;

But I wouldn't prefer either solution. Instead some small DC-DC switcher (uA78S40) with current limiting is better. You don't want to feed Vpp with > 1A (o;

 

[rkodaira]

problems on ua78s40

In some designs I have seen the use of a 7812 regulator plus 2 diodes connected at its common pin. Its gives 13.2V for Vpp. I think that it is a matter of what components the designer had available at the moment. Besides this fact all these components are easy to find and not expensive.

 

[alphi]

7808 is more cheaper than LM317,use resistor divider for 78XX adjust pin,use also can get any regulate voltage like lm317.
and all 78XX datasheet have such application example.

 

[CMOS]

The 7805/7808 solutions supplies also the 5V besides the 5V (o;

But I wouldn't prefer either solution. Instead some small DC-DC switcher (uA78S40) with current limiting is better. You don't want to feed Vpp with > 1A (o;

Any how you have to use two rgulators. One for 5V and one for 13V.

So its only matter of choice of components that these two designs have emerged. Isn't it?

 

[batdin]

My PIC programmer needs no external supply.It supplies itself from PC's RS232 connector.
It worked with every PIC I used.
Is there some reason to use a more complicated design?

 

[neelandan]

I have used a 78L05 for the +5 volts, and a series string of two zeners and a LED (just tried various combinations to get 13.5V) with a dropper resistor of 1K. A transistor shunts the zener combination to switch off the prog voltage.

It is just a matter of what components you have lying around, there are as many solutions as there are people.

 

[tgq]

I think 7805 + 7808 is bad solution because minimum worst case you can have 4.8+7.6=12.4V that is not enough especially if Vpp is transistor-controlled (0.6V lost => remains 11.8V)

 

[checkmate]

For things such as a PIC programmer, just obtain a correct design and implement it. There's not really much need to modify existing designs. It's your circuit that matters, not the programmer.
I used Patrick Touzet's ICD1 design which uses a charge pump design to impressively obtain 13V from a 5V. You can google around for the design, as everything from the schematics to the gerber is provided. The wonderful thing about running off 5v is that it can run off circuit power (where your PIC would require a 5V anyway), hence reducing the need of an additional power supply.

 

[xdev]

Hi, I use MC34063A step up 5V to 13V. It very good.
Khobkhun.

 

[maneco]

From my experience,i use EPIC ,built with information from the microcontrollers board...fast,works under xp,and supported by microcode...btw ,it uses lm 317 for 13v....

 

[stroma]

hi, i prefer mc34063a /or another dc-dc/ 5V to 13V step up conversion. then you can power the programmer with almost any wall AC adapter

best regards

 

[xdev]

Or you can use TL499A from TI but expensive than MC34063A (in my country).
Chokedee...