i.mx6ull Are there any regulations of voltage difference between VDD_ARM_CAP and VDD_SOC_CAP ?

[shaot]

We use i.mx6ull.

There is a description that "memory arrays domain voltage level should be kept equal to the rest of the core logic domains (Main, ARM)" in reference manual.

1. Does this description mean VDD_ARM_CAP and VDD_SOC_CAP should be equal ?

Reference manual p.366

Reference manual p.377

2. The typical value of VDD_ARM_CAP is 1.275. Is the typical value of VDD_SOC_CAP 1.275 too?

datasheet p.24

There is a regulation for the set voltage difference between VDD_SOC_IN and VDD_ARM_CAP (according to the following selected description), but there is no regulation for the voltage difference between VDD_ARM_CAP and VDD_SOC_CAP.

datasheet p.24

3. Is there a regulation for the allowable voltage difference between VDD_ARM_CAP and VDD_SOC_CAP?

We think that if 1. is correct, following set value is not correct. 

(e.g. The difference between VDD_ARM_CAP and VDD_SOC_CAP at 900MHz is 25000uV. not 0uV)

4. Would you tell me what is correct ? 

imx6ull.dtsi

cpu0: cpu@0 {
			compatible = "arm,cortex-a7";
			device_type = "cpu";
			reg = <0>;
			clock-latency = <61036>; /* two CLK32 periods */
			operating-points = <
				/* kHz	uV */
				900000	1275000
				792000	1225000
				528000	1175000
				396000	1025000
				198000	950000
			>;
			fsl,soc-operating-points = <
				/* KHz	uV */
				900000	1250000
				792000	1175000
				528000	1175000
				396000	1175000
				198000	1175000
			>;

https://github.com/varigit/linux-imx/commit/c3e4be705852c6d973d3b1f2b8b024fdea7303af

Would you answer 1. to 4. ?

Reference:
- Datasheet: "i.MX 6ULL Applications Processors for Consumer Products (REV 1.3)"
- Reference Manual: "i.MX 6ULL Applications Processor Reference Manual (REV 1) "
https://www.nxp.com/products/processors-and-microcontrollers/arm-processors/i-mx-applications-proces...

This question is related to https://community.nxp.com/t5/i-MX-Processors/What-will-occur-when-setting-i-mx6ull-VDD-SOC-CAP-at-90...

Best regards

[igorpadykov · Accepted solution]

Hi shaot

> 1. Does this description mean VDD_ARM_CAP and VDD_SOC_CAP should be equal ?

no.
That description is general description for arm power distribution system. i.MX6ULL has
not "ARM Memory array" subsystem.

>2. The typical value of VDD_ARM_CAP is 1.275. Is the typical value of VDD_SOC_CAP 1.275 too?

not.
Please refer to imx6ull.dtsi file it shows typical values.

>3. Is there a regulation for the allowable voltage difference between VDD_ARM_CAP and VDD_SOC_CAP?

no

>4. Would you tell me what is correct ? [..We think that if 1. is correct, following set value is not correct...]

a) referenced "imx6ull.dtsi" is correct
b) "1." is incorrect.

Best regards
igor

[shaot]

Thank you. 

[shaot]

@igorpadykov 

About the sentence "memory arrays domain voltage level should be kept equal to the rest of the core logic domains (Main, ARM)".

Would you tell me what voltage should be equal in Power Tree (Refrence manual p.360)?

[igorpadykov]

>what voltage should be equal in Power Tree (Refrence manual p.360)?

there are no such voltages, according to Table 10. Operating Ranges

i.MX 6ULL Applications Processors for Consumer Products

Reference Manual gives just generic desription, one needs to

follow particular datasheet description which prevails over Reference Manual.

Best regards
igor

[shaot]

Thank you for the information.