nrf52840 Rev 1 Errata DCDC Reg0 not working at all?

RE: nrf52840 Rev 1 Errata DCDC Reg0 not working at all?

Kenneth — Sun, 13 May 2018 11:09:48 GMT

I expect the fix will take place, there will be a product change notice a minimum 90 days before any change can take place, so I don't expect any fix to be available before late this year. These things take time to ensure that fixing one issue, don't have any negative impact on already existing designs.

RE: nrf52840 Rev 1 Errata DCDC Reg0 not working at all?

cjishnu — Thu, 10 May 2018 06:00:28 GMT

Hi, Any update on the discussion to fix Errata 197? Are there any plans to fix it soon?

RE: nrf52840 Rev 1 Errata DCDC Reg0 not working at all?

Kenneth — Wed, 25 Apr 2018 14:22:55 GMT

You should also see Errata-202 that apply to using REG0 with LDO or DCDC: "Do not draw current from VDD pin (external circuitry supply) during power up and ensure VDDH rise time is below 1 ms."

Note that there is currently an on-going discussion to fix both Errata-197 and Errata-202, I will know more in a few days.

RE: nrf52840 Rev 1 Errata DCDC Reg0 not working at all?

Atlas — Tue, 24 Apr 2018 13:38:22 GMT

In errata v1 - 3.29

- Symptoms : VDD voltage drop below specification when entering low power modes. Low voltage may trigger reset of device.

Conditions : Using DCDC on REG0, high voltage mode. DCDC on REG1 is not affected.

I don't use DCDC and want to use REG0 to set VDD output 1.8V in high voltage mode.

Does it trigger reset of device?

Thanks.

Atlas

RE: nrf52840 Rev 1 Errata DCDC Reg0 not working at all?

Kenneth — Mon, 26 Mar 2018 18:39:00 GMT

This issue have been partially masked by other issues that prevented low power mode when using VDDH for previous revisions. There is also more testing involved now where this problem was discovered.

Make sure to follow the schematic and layout for final hardware revision 1.

RE: nrf52840 Rev 1 Errata DCDC Reg0 not working at all?

Florian Zierer — Mon, 26 Mar 2018 17:16:10 GMT

Hi Kenneth,

this is really bad news for us. LDO vs DCDC is an efficiency problem (not good but at least it should work for now), but the external circuitry issue would be a show stopper!

One important question for us.

In the Revision Engineering A the supply of external circuitry was working. The errata does not mention this issue and on our testboard with a Rev A IC the startup and supply seem to work.

Was there really a degression from A to B or was it just that you increased some testing or some limits?

If the silicon behaves for external circuitry like Rev A, our schematics and layout should work.

RE: nrf52840 Rev 1 Errata DCDC Reg0 not working at all?

Kenneth — Mon, 26 Mar 2018 15:57:41 GMT

Hi,

If you require to support external circuitry (VDD from REG0) then you can't use DCDC on high voltage mode (VDDH) no. You can use LDO mode instead, with the power penalty that may give compared to DCDC, depending on the voltage difference between VDDH and VDD.

You should ensure that VDDH rise time is <1ms and that you have a gpio to control a mosfet to ensure VDD from REG0 is not powering external circuitry by default after reset.