MK24FN1M0VDC12R

[Veeking-Wu]

hello guys:

i'm veeking and i'm works in SKF group. now, we're developing a product based on MK24FN1M0VDC12R. about ADC function, there're some unclears in datasheet or RM doucument.

Q1: MK24 ADC reference voltage can use external volatge by VREFH pin and VREFL pin. 

in page 7 of datasheet. it descriptes the tolerant gap voltage ± 0.1V between VDD and VDDA.

VDD for MCU digital, VDDA for MCU analog. i didn't find the torlerant gap volatge between VREFH and VDDA. in my design, VREFL connect to VSSA. but my volatge for VREFH has a gap volatge to VDDA. gap volatge also is in ± 0.1V. is it risk for MK24? 

Q2: MK24FN1M0VDC12R is 121 pins package. in RM document, it said for VREF, user can select external VREFH/VREFL pair pins.  user also can select alternate reference pairt, that's VALTH and VATL. this pair may be additional external pins or internal sources depending on the MCU configuration. I had known that how to use internal 1.2V for alternate reference, but for external pins for VALTH and VATL, i didn't find. checked a serises in this familiy MCU. 141 pins package or 100 pins package, both of them don't have VALTH pins and VATL pins. what's wrong?

BR!

Veeking

[Pavel_Hernandez]

Hello, my name is Pavel, and I will be supporting your case, for the first doubt you could connect the VDD to the VDDA to get the same voltage even if this goes down will be done at the same time.

Deepens of your application in some cases the VREF is designed with a voltage divider in the PCB.

Let me research more about the last question.

Best regards,
Pavel

[Veeking-Wu]

Hi Pavel, thanks for ur supports. but the first question, i still not fully understand ur comments. i think i need to further explian my question. in our product, VDDA and VDD connect to same power source. however, VREF connects to another power source. VREF will have a ±0.1V gap with VDDA. in VREF section of datasheet, recommand VREF maximum is VDDA. not mention gap voltage between VREF and VDDA. only mention that gap voltage is ±0.1V between VDDA and VDD. so my question is what's gap voltage between VDDA and VREF?
about second question, waiting for ur good news. it's urgent for us. product is going to PCB, we found these two bugs and we need to get ur inform. to decide to if modify the SCH.
BR!
Veeking

[Pavel_Hernandez]

Hello, there is no gap there is only the maximum, at 3.3V, for example, the MCU cold works at 1.7V but your VREFH is 3.3V, the VREF is only for the ADC reference. 

Best regards,
Pavel

[Veeking-Wu]

hello Pavel:

As your said, maximum VREF of MK24 is 3.3V. power voltage for ADC reference keeps lower than 3.3V is ok. not depondes on VDDA. is it right?

about second question, do you have anthing to update?

[Pavel_Hernandez]

Hello, my apologies I did a double-check with my team when I asked for your last question. I´m afraid this MCU does not support what I said in the last message. 

The VREFH only supports as maximum what has the VDDA without a gap.

Pavel_Hernandez_0-1707241318892.png

Pavel_Hernandez_2-1707241500533.png

The variant does not support VATLH and VALTL.

Best regards,
Pavel

[Veeking-Wu]

Hi Pavel:

clear for me. when i deep read the MK24 datsheet, i found more bugs. hope you can explain these for me.

BUG 1: for MK24, operational temperature range is -40℃ to 10℃, but in Voltage reference electrical section (page 41 of datasheet), it said VREF limited-range operating temperature is 0℃ to 50℃, does it mean that internal VREF is only be used in this Temp. range, not full Temp. range?

BUG 2: DAC section (page 38 of datasheet), it said DAC reference can be selected to be VDDA or VREFH. but in reference manual, DAC reference only be selected to be VREFH or internal 1.2V.

can you clarify for above 2 bugs?

[Pavel_Hernandez]

Hello, I found the next information, I could not confirm the information that you mentioned with this datasheet.

Kinetis K24: 120MHz Cortex-M4F 1MB Flash (100-144pin) (nxp.com)

BUG 1: for MK24, operational temperature range is -40℃ to 10℃,

From MCU
Pavel_Hernandez_0-1708376807535.png

but in Voltage reference electrical section (page 41 of datasheet), it said VREF limited-range operating temperature is 0℃ to 50℃, does it mean that internal VREF is only be used in this Temp. range, not full Temp. range?

Pavel_Hernandez_1-1708376904680.png

BUG 2: DAC section (page 38 of datasheet), it said DAC reference can be selected to be VDDA or VREFH. but in reference manual, DAC reference only be selected to be VREFH or internal 1.2V.

RM

Pavel_Hernandez_3-1708378270315.png

Could you let me know if you have the last version of this documents? Let me know if the information is not helpful.

Best regards,
Pavel

[Veeking-Wu]

hi  Pavel:

as you found inform.,

BUG 1: for MCU, the operational temperature range is -40 to 105 degreeC. but for MCU VREF that's is MCU internal reference voltage 1.2V. VREF limited-range operating temperature is only 0 to 50 degreeeC. it made m confused. Shouldn't VREF be same as -40 to 105?

BUG 2: page 38 of datasheet, see below screenshot, I don't know why i have no permission to upload images.  "The DAC reference can be selected to be VDDA or VREFH" in page 38 of datasheet. you can search the previous words in datasheet and found it. as you can see your shared RM pitcture, DAC reference can be selected from VREF_OUT and VDDA.   RM doesn't match with datasheet. it's a error in datasheet or RM.

BR!

Veeking

[Pavel_Hernandez]

BUG 1: for MCU, the operational temperature range is -40 to 105 degreeC. but for MCU VREF that's is MCU internal reference voltage 1.2V. VREF limited-range operating temperature is only 0 to 50 degreeeC. it made m confused. Shouldn't VREF be same as -40 to 105?

Got it.

BUG 2: page 38 of datasheet, see below screenshot, I don't know why i have no permission to upload images.  "The DAC reference can be selected to be VDDA or VREFH" in page 38 of datasheet. you can search the previous words in datasheet and found it. as you can see your shared RM pitcture, DAC reference can be selected from VREF_OUT and VDDA.   RM doesn't match with datasheet. it's a error in datasheet or RM.

Pavel_Hernandez_1-1708396643259.png
Pavel_Hernandez_0-1708396633326.png

Just to confirm, is this the bug you mentioned?

Best regards,
Pavel

[Veeking-Wu]

Yes. difference on DAC reference voltage between datasheet and RM documents, i'm not sure is a descreption error or bug. from my  point, i think DAC ref voltage should has 3 options: VDDA/VREFH/internal 1.2V. but i don't know why has this error. if it's actual, which one is right? shall we following RM's descreption?

[Pavel_Hernandez]

Hello, sorry for the late response I have more comments, 

For the operation temperature range of VREF, I have checked with the design team, and VREF can work during the full temperature range of the device. Table 37 and Table 38 are just supplements to Table 35 and Table 36, it means that when the temperature range is 0-50 degrees, the range of Vout is 1.173-1.225V.

Pavel_Hernandez_0-1708979913089.png

For the DAC reference source, it should be VDDA and VREF_OUT, not VREFH. 

Best regards,
Pavel

[Pavel_Hernandez]

Hello, let me discuss this with my team when I get more information I will contact you.

Best regard,
Pavel