Kinetis 1.8 volts I/O

[luizmartins]

Hello.

I'm new to Kinetis and I need to communicate to a GSM module that runs at 1.8 volts.

How am I able to configure the FRDM-KL05Z board to use some I/Os at that voltage level?

I see that there is a reference to that supply voltage at the P5-9V_VIN pin but I'm not sure how to set it.

Could anybody help me with that?

I'd really appreciate it.

Many thanks!

[adriancano]

Hi,

The P5-9V_VIN pin is used to apply a source voltage to feed the board, this voltage enters to a 3V3 regulator to use this voltage as source of the Microcontroller.

The microcontroller can operate in two voltages range where the output voltage is defined here:

As you can see the Output voltage is VDD-0.5 of a pin in this two ranges of operation. According to this data you need to operate VDD at 2.3 V to meet 1.8 volts this when IOH = -1.5 mA. Running the microcontroller at the level 1.71 V <= VDD <= 2.7 V also make that all the input voltage coming from the module need to be at this range:

So, I recommend to you to run the microcontroller at the high level 2.7 V <= VDD <= 3.6 V and use a level shifter to manage the this voltage issues.

I hope this information can help you.

Regards,

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[luizmartins]

Adrian,

Thanks for your fast answer. But, how am I able to set VDD to 2.3 V ? I mean, at each pin / connection? When I'm using the FRDM-KL05Z board, I don't see this much flexibility at the reference manual.

It's not a problem to me to have all I/O to work @ 1.8 volts, actually this is good to me.

Thanks again!

[adriancano]

Hi,

As you can see in the picture of the schematic in my last answer there is a 3.3 Voltage Regulator. To feed the MCU with a different voltage you can use the battery input to source a voltage that is not regulated by the NCP1117 regulator.

Regards,

Adrian