nRF9160 DEC0 Pin and Decoupling Capacitors

[ShaunR]

I am currently working on a design with the nRF9160, and have a few questions about the DEC0 pin and decoupling for the module in general. I have been considering adding additional ceramic capacitors in the pF and nF range to the DEC0, VDD1 and VDD2 pins (to filter high frequency noise), but would like to know if this is recommended or not. My questions are as follows:

• Is the DEC0 pin used as decoupling for the power supply for the processor and peripherals, or is this pin used as decoupling for the power amplifier for the RF interface, or both?
• Is there any reason why I might want to add additional capacitance outside of the recommended 4.7 uF to the VDD1 and VDD2 pins, particularly capacitance in the pF and nF range?
• Are there any recommended capacitor specifications that should be considered when choosing these decoupling caps (ie. tolerance, voltage ratings, etc.)

Thanks in advance for any clarification!

[Andreas]

Hi,

 

We recommend that you replicate our reference design (both schematic and layout) as closely as possible. This is what we have based all internal boards for all kinds of testing and verification on, and on which all boards used for qualification and certification are based on.

See the HW integration guide here: https://www.nordicsemi.com/-/media/Software-and-other-downloads/SiP/nRF9160-SiP/nRF9160-Hardware-integration-guide.pdf

 

We do not have any nF or pF-range decoupling in our reference design, if you have reason to believe your supply is extra noisy you can add this yourself. It should not be needed, but as it also will not cause any issues it might add some confidence.

We have used 20% X5R components in our designs, if you want tighter tolerance or temperature rating than this that is fine.

 

Best regards,

Andreas

[ShaunR]

Hi Andreas,

Thanks for the response, and sorry for the delay in getting back to you. Sounds good about the decoupling capacitors, and capacitor specifications.

If you are able to share this information, it would be helpful to know what specifically the DEC0 pin is connected to internally on the module. Is this pin used for decoupling for the entire module, or is it used exclusively by some part of the module like the processor, or RF power amplifier, etc.?

Thanks,

Shaun

[Andreas]

Hi Shaun,

 

Unfortunately I am not able to disclose details about the SiP internals.

 

May I ask why you need this information? As far as we are concerned, you should load the DEC pin with the specificed capacitance, and not worry about it.

 

Best regards,

Andreas

[ShaunR]

Hi Andreas,

No worries, I understand!

The reason I ask is that I have seen other cellular module manufacturers choose a specific VDD pin as the power supply for the RF interface. In that case, I would maybe be inclined to add extra high frequency noise filtering in the form of smaller caps or a ferrite bead. I was wondering if there was a similar configuration for the VDD pins or DEC0 on the nRF9160.

Anyway, that answers all the questions that I have. Thanks again for the help!

Best Regards,

Shaun