ICD-U40 programming problems possible fix

[martin gordon]

I have been having problems programming some times with the ICD-U40 and have found a fix for all my current problems.

The problem seems to be related to EMC and stray high frequency paths.

The fix has been simple, to place a ferrite tube 28 mm long with an outside diameter of 14 mm and an inside diameter of 7 mm on the cable to the PIC. The cable is threaded through the ferrite twice.

This has fixed the problem on two different boards. The first has 4 PIC and two DC to DC converters that generate large amounts of interference.
The second board is a simple PIC with no other switching logic running.

The ferrite acts as a balan transformer, forcing the net currents to be zero. The lossy ferrite material attenuates the unbalance currents that the transformer action, did not balance.

Best to use ferrites made for EMC suppresion as they are lossy.

Split ferrites are available but usually donot work as well due to problems with the mating surfaces and resultant gaps.

My EMC work has not shown large difference between makes. Length does matter, longer the better.

Hope this helps with some problems.

Note this will not fix all problems such as wrongly set configurations bits etc


Martin

[wedilo]

Hello Martin,
Thanks for your information, but I'm surpriced. Are the ICDs not EMC compatible? It looks so.

73 Sven

[martin gordon]

I have no reason to believe that the ICD is not emc compliant (have not tested, but could).

But the ICD does have fast rise pulsed that usually go to PIC pins and hence unterminated. This could cause ringing.

The circuit usually has multiple 0 volt returns. This is due to power supplies, debug equipeement and the circuit that the PIC is intended to drive and a PC. The multiple earth return can cause signal degredation and cross talk between lines.

The action of the ferrite will be to clean up the signals.

Note the ferrite is on the cable between the ICD and the PIC

Martin

[bm919@hotmail.com]

[quote="martin gordon"]I have been having problems programming some times with the ICD-U40 and have found a fix for all my current problems.

The problem seems to be related to EMC and stray high frequency paths.

The fix has been simple, to place a ferrite tube 28 mm long with an outside diameter of 14 mm and an inside diameter of 7 mm on the cable to the PIC. The cable is threaded through the ferrite twice.

This has fixed the problem on two different boards. The first has 4 PIC and two DC to DC converters that generate large amounts of interference.
The second board is a simple PIC with no other switching logic running.

The ferrite acts as a balan transformer, forcing the net currents to be zero. The lossy ferrite material attenuates the unbalance currents that the transformer action, did not balance.

Best to use ferrites made for EMC suppresion as they are lossy.

Split ferrites are available but usually donot work as well due to problems with the mating surfaces and resultant gaps.

My EMC work has not shown large difference between makes. Length does matter, longer the better.

Hope this helps with some problems.

Note this will not fix all problems such as wrongly set configurations bits etc


Martin[/quote]