Load switch initial state

RE: Load switch initial state

vybz@gmx.de — Thu, 12 Jun 2025 13:29:37 GMT

Hi Bendik,

thanks for not forgetting me. And thank you very much for your time and support!

[quote userid="104202" url="~/f/nordic-q-a/122062/load-switch-initial-state/539043"]having C9 populated on revision Fxx and later will not be an issue as the pin have been disconnected internally.[/quote]

That's a valuable point. This means following the paradigm "better safe than sorry" will be quite cheap in this case. I was also not aware that the "F" in the device's ID code refers to that revision. Because the docs identify "F" as "firmware" (pre-programmed). But then the document reference you have provided is pretty explicit on how to identify the revisions that have implemented the update.
Thanks for clarifying on that.

You have helped me very much. Thank you! Good to have you around ;)

I wish you a great day!

Best regards,
Brian

RE: Load switch initial state

Bendik Heiskel — Thu, 12 Jun 2025 12:42:58 GMT

Hi Brian,

[quote user="vybz@gmx.de"]Can we safely drop the N.C. parts C13, C10 from the design, especially from the PCB? Because there is no explanation why for example the DEC2 is not requiring that external decoupling capacitor and why it is still in the reference design.
[/quote]

C13 and C10 can be removed, they are left as placeholders to show that the DEC2 pin should be left floating, and that the capacitors on the DEC4_6 net should all be placed close to the DEC4 pin, and not close to the DEC6 pin.

[quote user="vybz@gmx.de"]

Additionally, the reference design coontains a capacitor C9 for DEC5 with the note "not required for Fxx or later". How can I know the build ID in advance? Can we safely assume that all parts that are curently available from major distributors satisfy that condition (because pre Fxx builds are older than e.g.10 years? Is it safe to drop C9 from the design?

[/quote]

The Fx0 revision of the nRF52840 was introduced in 2021, it has a separate ordering code nRF52840-QIAA-F so as long as you are ording the correct part it should be OK to remove C9.

If you want the option to use older revisions you need to keep C9, having C9 populated on revision Fxx and later will not be an issue as the pin have been disconnected internally.

The change is documented in Information Notice 141

Best regards,

Bendik

RE: Load switch initial state

vybz@gmx.de — Fri, 06 Jun 2025 13:39:51 GMT

Hi Bendik,

Thanks for that clarification. I was really hoping that the nPM1300 implements that behavior to make a discrete load switch obsolete.

I have a different question I hope you can help me with.
I have based the discrete design for the nRF52840 on the latest reference design.

Can we safely drop the N.C. parts C13, C10 from the design, especially from the PCB? Because there is no explanation why for example the DEC2 is not requiring that external decoupling capacitor and why it is still in the reference design.

nRF52840 reference design (config. 7)

Best regards,
Brian

RE: Load switch initial state

Bendik Heiskel — Thu, 05 Jun 2025 13:58:05 GMT

Hi,

The states of the load switches on the nPM1300 are only controllable though the TWI interface, by default the load switches are disabled.

The nPM1300 alone can not achieve your desired functionality, the simplest solution I can see is using external load switches where one is by default enabled using pull resistors.

Best regards,

Bendik