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

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

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robotjosh
Contributor IV

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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jamesmurray
Contributor V

josh.outerspace

How did this work out?

James

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xiangjun_rong
NXP TechSupport
NXP TechSupport

Hi, Josh,

Regarding the voltage transceiver circuit, I do not know why you use the MOSFET ZVN3310A to implement the voltage transceiver function, you do not need power in your application I suppose.

I suggest you use external OC gate(Open Collective) such as 74LS07, you can also use 74LS244 buffer circuit with 3.3V power supply, it is okay.

As an alternative, I think you use use NXP buffer for example 74HC3G16 or 74HCT3G16, this is the website:

Have a merry Christmas day.

BR

Xiangjun Rong

http://cache.nxp.com/documents/data_sheet/74HC_HCT3G16.pdf?pspll=1

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