i.MX 6SoloX PMU_LOWPWR_CTRLn Register Question

[albert_han]

Hi, 

In the middle of 24MHz xtal start-up timing investigation, I found our SW configures RC_OSC_EN bit [0] in PMU_LOWPWR_CTRLn register as 0 which means it uses RC OSC for 24MHz clock source. 

In the SW source code, I found the following comments. 

"In low power idle mode, 24MHz XTAL power will be off and 24MHz clk source will be switched to RC-OSC to save power, this feature is only enabled on i.MX6SX TO1.2."

I thought our HW and SW designed for using a discrete 24MHx xtal as the 24MHz clock source. but this configuration and comment confuse me. 

When we change the bit to 0 so that we use XTAL OSC for 24MHz, what potetial impacts we would consider?

Power consumption is not at critical factor in our application.

Regards,

Albert

[Yuri]

Hi,

  24 MHz RC_OSC also has low accuracy. But this is not so important as for 32 KHz,
since 24 MHz does not affect real time clock. 

Regards,
Yuri.

[Yuri]

@albert_han 

Hello,

 The main disadvantage of the internal RC OSC is its low accuracy.
When a high-accuracy real-time clock is not required, the system may
use the on-chip 40 kHz oscillator. The tolerance is ± 50%.   

Regards,
Yuri.

[albert_han]

Hi, Yuri

My question is related to 24MHz clock source setting in the register of PMU_LOWPWR_CTRLn (0x020C8270), Bit No. 0 (RC_OSC_EN). 

Is this bit for 32KOSC clock source? And the comment on DRM is a typo?

Regards,

Albert