PicKit 2 FULL with TH components - Need help with layout

[Computerman29]

pickit 2 vpp voltage level error

Greetings All,

I drew the original schematic for the PicKit 2 into Eagle using all through-hole components. I substituted the dual MOSFET with discrites, and replaced the op-amp with a through hole version. All of the other parts are identical to the original (just through-hole).

The problem is when I built the circuit, the device connects and is recognized by both MPLAB and PicKit software, but it disconnects randomly, the PicKit software detects either a short in Vdd, or Vdd=0V. Sometimes it reads correctly. Vpp is all over the place. Again, sometimes it reads correctly. When I test it with my meter, everything reads correctly. MCLR on/off works properly. 30kHz toggle works properly on both the PGC and PGD pins. I am also able to store a unit ID, but it will not calibrate. Vdd reads 4.26V on my meter.

I am pretty sure the schematic is correct. Maybe the MOSFET's and/or op-amp are too slow? I think it is the layout. The only way to keep it single-sided was to add several jumper wires and I think that added too much capacitance.

I am relatively new to designing PCB layouts. I dealt mainly with perfboard (hobbyist style). If somebody more experienced than I in designing layouts could assist me I would be most grateful. I will post my Eagle files. Thanks.

 

[rkodaira]

pickit2 vpp voltage level error

Hi !

I could not see the files you posted, but I wonder what are the through hole discretes replacement mosfets you used instead of smd parts (I tried to find some mosfets with the same specifications of the mosfets used in the PICKIT2 original circuit, but I was not well succeded).

Returning to your problem: maybe your USB port cannot supply enough current to your PICKIT2 circuit. Have you used the decoupling 100nF capacitors near the supplying pins of the 18F2550 ?
Are the replaced mosfets electrically equivalent to the original mosfets ?
I think long wire jumps will not harm the functioning of the circuit (but i couldn´t see the layout).

 

[Computerman29]

pickit 2 vdd voltage level error

OOPS!!! I forgot. Thanks.

I soldered a 100nF 0805 between power pins on the bottom of board. It now passes all tests, but it still won't calibrate.

The software reads Vdd= 4.1v Vpp=Vdd on 3v devices and Vdd= 4.5v Vpp=11.9v on 5v devices.

My meter reads Vdd=4.23v Vpp=Vdd on 3v devices and Vdd=4.61v Vpp=12.04v on 5v devices.

Vdd seems a bit high for 3v devices, but the software says it passes.

BTW, the MOSFET's are ON Semiconductor. The N-channel is p/n:NTD3055L104 The P-channels are p/n:NTD20P06L. The op-amp is Microchip p/n:MCP6271-E/P.

The .zip file opens with Winzip or WinRar. The .sch and .brd files open with Cadsoft Eagle.

 

[mvs sarma]

pickit2 layout

Please check for proper polarity of pins of the MOSFETs used. while soldering some reversals possible. ensue this aspect
I could do the crosscheck of layout and the schematic if you could mail me directly at mvs_sarma(at)yahoo.com

oops! I may not have Eagle, but i will try to load it

Added after 1 hours 59 minutes:

OOPS!!! I forgot. Thanks.

I soldered a 100nF 0805 between power pins on the bottom of board. It now passes all tests, but it still won't calibrate.

The software reads Vdd= 4.1v Vpp=Vdd on 3v devices and Vdd= 4.5v Vpp=11.9v on 5v devices.

My meter reads Vdd=4.23v Vpp=Vdd on 3v devices and Vdd=4.61v Vpp=12.04v on 5v devices.

Vdd seems a bit high for 3v devices, but the software says it passes.

BTW, the MOSFET's are ON Semiconductor. The N-channel is p/n:NTD3055L104 The P-channels are p/n:NTD20P06L. The op-amp is Microchip p/n:MCP6271-E/P.

The .zip file opens with Winzip or WinRar. The .sch and .brd files open with Cadsoft Eagle.

IT IS TOLD THAT LATER VERSIONS OF SOFTWARE DON'T HAVE THE CALIBRATION FACILITIES, THAT VER1.1 OR SOME VERSION HAD.
PLEASE READ THE picKIT2 RELATED INFO ON THE MICROCHIP FORUM

 

[mvs sarma]

pickit2 oscilloscope

The ver2.40 still has the voltage calibration function.

Thanks FunnyNYPD

 

[rkodaira]

pickit2 full

Check that the IRLML6402 mosfet replaced by the NTD20P06 is the voltage regulator element that makes the target Vdd variable. It acts as a variable resistor controlled by the amp op that has input coming from a PWM signal filtered by a RC network. Any difference in the specification of these mosfets can result to a different behavior of the voltage Vdd, not working as designed/programmed.

I did a fast read on the datasheets and I found some differences (for example: Threshold Vgs and on resistance).

Maybe using the correct parts or changing the feedback network resistors (e.g. R28) to a new adequate value will make a solution.

 

[Computerman29]

pickit2 2n7000

I did some more tests and discovered that the output from the op-amp (the input to the NTD20P06) is 5.11v when 3v devices are selected and 3.66v when 5v devices are selected. Also, the datasheet of the NTD20P6 shows the gate threshold to be 1.5v compared to the .6v of the original part. The input and output capacitance is also slightly higher.

Also:
Are the originals logic level?

Are the originals enhancement mode?

 

[Computerman29]

pickit2 components

I posted the wrong layout file!! The one I posted first is ripped up. This one is fully routed.

 

[nishal]

irlml6402 microchip

Hi Computerman29,
can U post pdf version of the schematic. If you need I will try to reroute the pcb.

thanks

Nishal

 

[Computerman29]

pickit2 eagle

SUCCESS!!!!!!!

I have discovered the problem. There is an error in my schematic. The drain and source of Q1 are reversed. The unit now calibrates and is fully functional!!! WOO-HOO!!!!!

Many thanks to all who helped. Special thanks to rkodaira for steering me in the right direction. I will post a corrected version of the .sch and .brd files and also a .pdf. Please feel free to improve the layout as needed.

Peace,
Computerman29

Added after 1 hours 52 minutes:

Here are the CORRECTED .sch and .brd files as promised. I cannot make .pdf files. Enjoy!

 

[Computerman29]

pickit2 vdd voltage error

There is one more thing that I think I should point out to anybody who builds this:

OBSERVE THE POLARITY OF THE TRANSISTORS VERY CAREFULLY!!!!!!

The transistors in the circuit are ECB (not EBC like most others). They could easily be changed to avoid confusion or if BC639's and/or BC640's are unavailable locally. The only reason I used those transistors is because I was out of the 2N3904/2N3906's that I normally use. Have fun!!

Peace

 

[mvs sarma]

pickit2 eagle files single sided

There is one more thing that I think I should point out to anybody who builds this:

OBSERVE THE POLARITY OF THE TRANSISTORS VERY CAREFULLY!!!!!!

The transistors in the circuit are ECB (not EBC like most others). They could easily be changed to avoid confusion or if BC639's and/or BC640's are unavailable locally. The only reason I used those transistors is because I was out of the 2N3904/2N3906's that I normally use. Have fun!!

Peace

Did you make a single sided PCB with all red wires hand wired with jumpers?
BTW, I have already indicated the need for checking the FET polarities in my post dated 28-2-08. That should be valid even for Transistors.
Congrats that you have made to work.

Sarma

 

[Computerman29]

how to rectify vpp error in pickit 2

Did you make a single sided PCB with all red wires hand wired with jumpers?

Yes. That is correct. Quite a lot of jumpers, but it kept it single-sided. They seem to go all over the place, but I did not want to cross them and cause drc errors and other problems. Perhaps you or somebody else could do better. Like I said before, I am somewhat new to PCB layout design (but not to electronics).

I have already indicated the need for checking the FET polarities in my post dated 28-2-08. That should be valid even for Transistors.

Yes you have, and it was that tip and rkodaira's mention of the function of Q1 that led me to the problem. Many thanks to both of you!! I was merely stating that the transistors in the schematic and layout use a different pinout than most general purpose transistors.

Congrats that you have made to work.

Thanks.

 

[mvs sarma]

layout pickit2

Did you make a single sided PCB with all red wires hand wired with jumpers?

Yes. That is correct. Quite a lot of jumpers, but it kept it single-sided. They seem to go all over the place, but I did not want to cross them and cause drc errors and other problems. Perhaps you or somebody else could do better. Like I said before, I am somewhat new to PCB layout design (but not to electronics).

................

Nice that being a newcomer to Eagle, you have taken up a large project and DID WELL I would say.

Appreciable

Sarma

 

[lee40039]

bs250 substitute

L IS 680UH?

 

[Computerman29]

nishal’s pickit2

L IS 680UH?

Yes it is.

 

[wakaka]

pickit 2 vdd and vpp voltage level errors

Hi TS, can u translate the schematic and layout to pdf format as i dun have eagle. Or to a gif file?
THere is free pdf translator available, which is pdf995.
thanks.

 

[scabreram]

pickit2 mosfet transistor problem

Thank you very much

 

[mvs sarma]

pickit2 wire color

Hi TS, can u translate the schematic and layout to pdf format as i dun have eagle. Or to a gif file?
THere is free pdf translator available, which is pdf995.
thanks.

It would be better to install and use Eagle-The job wold be done and you learn too. the PDF converters carry some distortion as I experienced personally. Re-sizing would be a problem.

 

[wakaka]

pickit2 calibration

i dun prefer to install eagle as I'm using protel now. So can anyone help? thanks.