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Pin migration between K21_50 MHz and K21_120 MHz devices in the 121-MAPBGA package

Question asked by Michael Goudey Employee on Dec 22, 2014
Latest reply on Dec 26, 2014 by Hui_Ma

I am considering pin migration between 50MHz and 120MHz K21 devices in the 121-MAPBGA packages.  It appears the 120MHz device pinout is a superset in many ways so shared features should be available with a single board design.  There are a couple of questions though:

 

(1) K21_120 includes an extra VDD/VSS pair in the 121-MAPBGA package.  These are NC pins on the K21_50 device.  How should I design a board to accommodate both devices?  Can the NC pins be connected to VDD/VSS for the 50MHz device?

(2) Are there any considerations for clocking to support both devices?  I realize FEI (FLL-Enabled Internal) mode won't accommodate 120MHz operation, so I believe I should populate an external crystal.  Is there any preference for frequency?

 

Thanks,


Michael Goudey

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