topic Re: Voltage range on VREFH pin of kinetis MK10DX64VLH7 in Kinetis Microcontrollers

Voltage range on VREFH pin of kinetis MK10DX64VLH7

rolandve — Thu, 10 Jul 2014 08:45:58 GMT

Dear all,

I'm using an external reference voltage connected to the VREFH pin of the kinetis microcontroller. The total supply current should be very low, so I want to be able to shutdown the external reference when I don't need it and continu to use an internal reference. The problem is that the minimum voltage on the VREFH pin is specified as 1.13V and the voltage will drop below this when the external reference is disabled. So the question is, do I need to make sure that the voltage on VREFH is always above 1,13V or may it drop below this when using an internal reference and does this requirement change when not using the ADC at all?

With kind regards,

Roland

Re: Voltage range on VREFH pin of kinetis MK10DX64VLH7

chris_brown — Thu, 10 Jul 2014 15:28:19 GMT

Hi Roland,

Very interesting situation. Just wanted to let you know that I have reached out to our analog team to investigate this. Hopefully I will have a response soon.

Regards,

Chris

Re: Voltage range on VREFH pin of kinetis MK10DX64VLH7

chris_brown — Fri, 11 Jul 2014 14:44:44 GMT

Hi Roland,

From our analog team:

When the external VREFH pin is not selected, it can be any value. It should not be hard-tied to ground for latch-up reasons, but if it floats to ground it is OK.

So I guess the real question is, will the external reference hard tie the pin to ground or will it let it simply float below 1.13V?

Regards,

Chris

Re: Voltage range on VREFH pin of kinetis MK10DX64VLH7

rolandve — Mon, 14 Jul 2014 06:05:01 GMT

Hello Chris,

Thank you for your answer, this really helps. I do not yet know if the external reference will pull the pin hard to ground, but if it does a small mosfet in series with the external reference should help to decouple it from the vrefh pin.

With kind regards,

Roland