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PostPosted: 24 Nov 2011 11:08 
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Joined: 24 Nov 2011 10:36
Posts: 3
Hi folks,

I am currently using a set of ME Lin boards, an LV18Fv6 with a P18F67J60 and a couple of P16F887 Ready for pic boards to create a Lin network. All the boards are connected to LIN transceiver boards via RC2,RC3, RC6 and RC7. The Lin Master is the LV18Fv6 board.

As the MCP201 parts are going obsolete I replaced the MCP201s on a couple of the boards with MCP2021s however I am having trouble with unstable Vreg and the transceivers get VERY hot. Communication with the hot nodes still seems to work fine.

To adapt the boards I simply replaced the MCP201s with MCP2021-500s and removed the slope selection jumper, I can't see any further hardware modifications that are required. I am running the Lin bus at approximately 12V.

I have found that if I swap the boards around so that an MCP2021 is the master, the master MCP2021 will not get hot.


Does anyone have any idea where I may be going wrong?

Do the MCP2021 pieces naturally run very hot?


If anyone can offer any advice or would like to know more I look forward to hearing from you.

Cheers,
M


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PostPosted: 25 Nov 2011 12:52 
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Joined: 24 Nov 2011 10:36
Posts: 3
Hi again,

Eventually realised the problem was due to instability in the voltage regulator.

The load capacitor (C2) should be 8 - 10 times the size of the input capacitor (C1), on the ME board both capacitors are the same size (100n). Swapping C2 for a 10u cap fixes the problem. The selection seems to be tolerated on an MCP201 but cause big poblems on a MCP2021.

ME LIN board reference : http://www.mikroe.com/eng/downloads/get ... l_v100.pdf
MCP201 datasheet : http://ww1.microchip.com/downloads/en/D ... 21730F.pdf

M


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