Troubleshooting HF clock that is not starting

RE: Troubleshooting HF clock that is not starting

Jared — Fri, 22 Apr 2022 11:37:42 GMT

Hi Mark,

[quote user="mark.blackburn.orpyx"]We haven't characterized are failures to this detail yet. There may be other failures like this but I haven't confirmed. We have other units where the radio (BLE) is not working, but haven't confirmed if the crystal oscillator is the cause. Do you have an idea how often this might occur?[/quote]

This isn't a common problem so I don't really have any numbers on this, and I'm still not sure if the problem is the IC itself. Have you tried changing the load capacitors for the other units that doesn't work?

[quote user="mark.blackburn.orpyx"]I don't have that capability without taking the board to our contract manufacturer. I'll perhaps reassess if we think this is occurring often enough to do that work.[/quote]

Ok.

regards

Jared

RE: Troubleshooting HF clock that is not starting

mark.blackburn.orpyx — Wed, 20 Apr 2022 20:14:17 GMT

> What percentage of samples produced is affected by this?

We haven't characterized are failures to this detail yet. There may be other failures like this but I haven't confirmed. We have other units where the radio (BLE) is not working, but haven't confirmed if the crystal oscillator is the cause. Do you have an idea how often this might occur?

> Could you try changing the IC from a working sample to a non-working sample and see if it fixes the problem?

I don't have that capability without taking the board to our contract manufacturer. I'll perhaps reassess if we think this is occurring often enough to do that work.

RE: Troubleshooting HF clock that is not starting

Jared — Tue, 19 Apr 2022 07:34:46 GMT

Hi,

What percentage of samples produced is affected by this? Could you try changing the IC from a working sample to a non-working sample and see if it fixes the problem? It could help us understand what's causing this.

regards

Jared

RE: Troubleshooting HF clock that is not starting

mark.blackburn.orpyx — Fri, 15 Apr 2022 13:36:02 GMT

I tried changing the crystal. It still won't start.

RE: Troubleshooting HF clock that is not starting

Jared — Mon, 11 Apr 2022 07:46:49 GMT

Hi,

[quote user="mark.blackburn.orpyx"]

Should I suspect that something is wrong with the crystal, capacitor or their soldering? Or could something be wrong with the XC2 pin on the IC?

[/quote]

I would suspect either the crystal or the soldering. Have you tried changing the crystal on the PCB?

[quote user="mark.blackburn.orpyx"]Yes, the load capacitance of the crystal is 10 pF[/quote][quote user="mark.blackburn.orpyx"]There are 2 12 pF load capacitors connected to the XC1 and XC2 pins and to ground.[/quote]

Then the crystal isn't properly loaded. The parallel load capacitors should be 16 pF if the internal load capacitance is 10 pF. However, I don't think this is the culprit in your case. But it would be good to change them to the correct size later.

regards

Jared

RE: Troubleshooting HF clock that is not starting

mark.blackburn.orpyx — Fri, 08 Apr 2022 20:22:53 GMT

> Seems like XC2 line isn't driven high for some reason.

Should I suspect that something is wrong with the crystal, capacitor or their soldering? Or could something be wrong with the XC2 pin on the IC?

Yes, the load capacitance of the crystal is 10 pF..

RE: Troubleshooting HF clock that is not starting

Jared — Fri, 08 Apr 2022 10:44:06 GMT

Seems like XC2 line isn't driven high for some reason.

[quote user="mark.blackburn.orpyx"] FA-128 32.0000MF20X-K5.[/quote]

The part number didn't quite match the expected form that is described in the datasheet:

Is the internal load capacitance of the crystal 10 pF?

regards

Jared

RE: Troubleshooting HF clock that is not starting

mark.blackburn.orpyx — Thu, 07 Apr 2022 22:57:31 GMT

For comparison here is a working oscillator on the the nRF52840 DK

RE: Troubleshooting HF clock that is not starting

mark.blackburn.orpyx — Thu, 07 Apr 2022 22:26:56 GMT

This is what I see if I probe XC1 and XC2 when the firmware does NRF_CLOCK->TASKS_HFCLKSTART = 1

Trace 1 (Yellow): XC1

Trace 2 (Blue): XC2

RE: Troubleshooting HF clock that is not starting

mark.blackburn.orpyx — Thu, 07 Apr 2022 17:36:17 GMT

The crystal part number is FA-128 32.0000MF20X-K5. There are 2 12 pF load capacitors connected to the XC1 and XC2 pins and to ground.

Datasheet is here: support.epson.biz/.../doc_check.php

RE: Troubleshooting HF clock that is not starting

Jared — Thu, 07 Apr 2022 11:19:31 GMT

Hi,

What do you see if you probe the XC2 and XC1 lines, do you see a oscillating signal? Could you provide the full part number and datasheet of the crystal that you're using? And also provide the size of the parallel load capacitors?

regards

Jared