VREFH for S32K324

[hemanths]

Hi NXP Team,

I am using the S32K324 microcontroller operating at 3.3V for my circuit. The VREFH pin in the microcontroller is connected with 3.3V (VDD_HV_A / VDD_HV_B) itself. In the datasheet, I saw a note regarding the VREFH voltage levels.

hemanths_0-1688361073670.png

But in the hardware design guidelines document this comment is not mentioned.

hemanths_1-1688361175410.png

Can somebody please explain the significance of the note mentioned in the datasheet.

Thanks & Regards

Hemanth 

[JulesW]

What if the VREH is much lower than VDD_HV_A, typically VREFH = 2.5V for a VDD = 3.3V?

[danielmartynek]

HI @JulesW,

That would be out of specification, as VREFH is limited to a minimum of 2.97 V according to the datasheet (Table 3, Operating Conditions).

BR, Daniel

[danielmartynek · Accepted solution]

Hi Hemanth,

The VREFH reference does not have to be connected to VDD_HV_A / VDD_HV_B.

But the reference is clamped to VDD_HV_A, therefore, the voltage must not exceed VDD_HV_A + 0.1V, and the 0.1V is for RF signal only.

In the HWDG rev.C, you can find the specification too:

danielmartynek_0-1688380987606.png

Regards,

Daniel

[hemanths]

Hi Daniel,

Thanks for the response.

What happens if the input voltage of an ADC is greater than the VREFH of the ADC? Whether the microcontroller's ADC have any overvoltage protection or saturation mechanisms?

[danielmartynek]

The ADC result would be saturated.

The injection current must be limited to 3mA per a pin.

danielmartynek_0-1688384914242.png

danielmartynek_1-1688385147391.png

BR, Daniel