MWCT2D16S FXOSC ISSUE

[Devin51]

We use MWCT2D16S in WPC, use 20MHz as external crystal and have some questiones as below:

1.Is EXTAL_SWING_PP a requirement for the amplitude of the external crystal input?

2.The parameter EXTAL_SWING_PP varies depending on whether ALC is enabled or disabled. In which register is the enable/disable of ALC configured in the software?

3.Under what circumstances should ALC be enabled? Under what circumstances should this function not be enabled?

4.The extal_swing_pp is  0.5V, is okay for our system?

[danielmartynek]

Hello @Devin51,

1.

Yes, the minimum and maximum values should not be exceeded.

2.

In FXOSC Control Register (CTRL).

3.

ALC stands for automatic level controller and it is a feature that controls the power delivered to the output of the FXOSC amplifier to keep it as constant as possible. ALC is enabled by default. Disabling it increases the Vpp swing (potentially increasing EMI) and the power consumption.

4.

It is within the specification.

There is no need to have the 1M feedback resistor.

Refer to the S32K3 HW design guidelines:

https://www.nxp.com/webapp/Download?colCode=S32K3_HW-DesignPackage

Regards,

Daniel

[Devin51]

Hi Daneil

Thank for your reply,

1. In the MWCT2XXXS Reference Manual (RM), the FXOSC Control Register does not have an ACL control bit. This is different from the S32K3xx Reference Manual.
2. Is a 1MΩ resistor integrated in the MCU? In our design, we usually place this resistor externally.