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How to convert 3.3V freedom board to debug 5V target?

Question asked by Josh Jordan on Dec 22, 2015
Latest reply on Dec 25, 2015 by xiangjun.rong

I'm using the FRDM-KE02Z40 for a project that runs on 5V and need to debug it.  There are 4 signals to convert- target power, dio, clk, and reset.  For target power I put a 3.3v regulator there so 5V on that line shows 3.3V to the debugger.  I left the clock the same since it is one way and 3.3V should be ok with 5V logic.  For dio and reset I made a bidirectional level shifter with the ZVN3310A N-channel mosfet where the gate is connected to 3.3v, source to the 3.3v logic side, and drain to the 5v logic side, and used 1.5k pullups on each side of both level shifters.  The problem is the level shifter bandwidth is not high enough for the DIO signal.  I am seeing slight differences between sides of the level shifter on the DIO signal.

 

Is there a better way to do this?  Are there better mosfets designed to be bidirectional level shifters?

 

Thanks!

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