In S32K144 what is the difference between VDDA and VREFH?

[andrearicca]

I want use the S32K144 to sampling some analog signals. In my project I have 2 different voltage regulators at 5V and I want use the first regulator to supply the microcontroller (VDD pin) and the second regulator as ADC reference supply. From the datasheet (S32K1XX) I see that the pin VDDA (Analog supply voltage) is shorted to VDD. Instead the pin VREFH can be connected to the second voltage regulator or this three voltages must be shorted together to only unique voltage regulator? I not understand the difference between the pins VDDA and VREFH, because in the "Hardware design guidelines for S32K1xx" (AN5426, pag 2) the 3 pins are shorted together.

Thanks.

[danielmartynek]

Hi,
VDDA and VDD must be shorted on PCB, but VREFH can be connected to another source.
There is a restriction, VREFH should be equal or less than VDDA + 0.1V and VDD + 0.1V.
Please see Table 2 in S32Kxx DS rev.6
S32K144EVB allows to select the sources of VREFH.

Regards,
Daniel

[lohrsistemas]

Hello,

Can I put:

VDD1,VDD2,VDD3,VDD4 in 3V3

and

VDDA,VREFH in 5V?