iMXRT117x clock root: why so many peripherals selected internal 48Mhz RC clock as root?

[TCL_1]

Hi,

I'm talking about this SDK: Processor 'MIXRT1175xxxxx', version V2. 12.1.

My questions are:

1. Why so many peripherals selected internal 48Mhz RC clock as root? e.g. FlexSPI1 clock root, ADC1 clock root, MIPI_REF clock root and so on.

2. Why didn't select the precise external oscillator 24Mhz clock?  What are the main advantages and disadvantages?

3. If i want config all the peripherals to select oscillator 24Mhz clock root (by config tools MCUXpresso), currently i have to config one by one, is there any method to config by batch?

many thanks!

[jay_heng]

Internal RC48M is one of clock root option, it is mainly used for lower power case. and it's also not very accurate

you have to configure it one by one in MCUX CFG tool so far.

[mjbcswitzerland]

Hi

I made this table to make it easier to see which sources can be used by each peripheral.

Regards

Mark

[TCL_1]

Hi Mark,

Thanks for your sharing.

Do you know the mainly differences between OSC24M and RC48M_DIV2? power consumption or what? I just wonder why the SDK use RC48M_DIV2 as clock root of most peripherals, is there any benefit that change it to OSC24M source? 

I guess there's no standard answer, just discussion. thank you again.

BR

Tyrone

[mjbcswitzerland · Accepted solution]

Hi

I would use OSC24M instead of RC48M_DIV2 if you want 24MHz, and you do have the 24MHz attached (which is almost always the case).

The 24MHz oscillator will be very accurate (eg. 10ppm) whereby the RC48M_DIV2 is derived from a trimmed RC oscillator, which will be less accurate (2%) and have more temperature drift.

Regards

Mark

[TCL_1]

well i ignored the accurate difference between the OSC24M and RC48M_DIV2, but RC48M_DIV2 should be ok for low-speed peripherals, since SDK did that. Then, still the question, why not OSC24M?