About Clock on PCA9450.

[mark_kim]

Dear

I would like to ask for your advice on the following while designing the circuit using i.mx8 plus PCA9540C.

1) In the datasheet, the source of 32.768KHz Output is either external Crystal or internal 32khzoscillator. Is there a difference in the characteristics of the 32KhZ output depending on the two clock sources?

2) If you look at the I.MX8 PLUS reference circuit, it is recommended to use eXTERNAL Crystal, but does it not affect the output of ldo and dcdc of pca9540c when using the internal 32khzoscillator?

3) When using the internal 32Khzoscillator, is there any other precautions besides connecting the external crystal to GND and treating XTAL_OUT as Floating?

thank you for your consideration

Best Regards

Mark Kim

[mj-123]

Hi,

may I add a question to this topic as it fits here.

In the reference design for the i.MX8M Plus, a 32.768KHz crystal is provided for both the processor and the PMIC PCA9450.

However, as far as I understand, there is also the possibility to:

1. Operate the PMIC without an external crystal and only connect a crystal to the processor.
2. Connect an external crystal to the PMIC and pass the signal via CLK_32K_OUT to the processor.

What would be the preferred way, respectively what are the advantages?

Thanks,
Manuel

[guoweisun]

• In the datasheet, the source of 32.768KHz Output is either external Crystal or internal 32khzoscillator. Is there a difference in the characteristics of the 32KhZ output depending on the two clock sources?

[gw]The specification parameter is different for example:

guoweisun_0-1620355174708.png

2) If you look at the I.MX8 PLUS reference circuit, it is recommended to use eXTERNAL Crystal, but does it not affect the output of ldo and dcdc of pca9540c when using the internal 32khzoscillator?

[gw]No affect.

3) When using the internal 32Khzoscillator, is there any other precautions besides connecting the external crystal to GND and treating XTAL_OUT as Floating?

[gw]No.

[mark_kim]

Dear 

Could you let me have your advice ?

thank you

Best Regards

Mark Kim