Unexpected Wakeup from Hibernate Mode via SHPHLD with Rising-Edge Configuration on nPM2100

RE: Unexpected Wakeup from Hibernate Mode via SHPHLD with Rising-Edge Configuration on nPM2100

Kazi Afroza Sultana — Wed, 10 Dec 2025 16:00:21 GMT

Thanks Philipp. we will try to clarify this mechanism on the next version of Product documentation.

RE: Unexpected Wakeup from Hibernate Mode via SHPHLD with Rising-Edge Configuration on nPM2100

vielleicht — Thu, 04 Dec 2025 12:57:18 GMT

Hello,
thank you for the time you spend on the clarification and for reproducing the behaviour on your side.

Based on your feedback and our own testing, we now understand the SHPHLD wake-up mechanism as follows:

The SHPHLD input is synchronized and debounce-filtered.
This means the pin is sampled and evaluated on its level, not on an asynchronous transition.
If the pin is already in the active level when entering Hibernate, the nPM2100 wakes immediately, even though no edge occurred. This confirms that the mechanism is fundamentally level-triggered, not event-driven.
If the pin changes level during Hibernate, this may look like an edge-triggered wake-up, but only because the sampled level changed between sampling points — not because an actual edge detector exists.

From this, it becomes clear that the wake-up mechanism is always level-based, and the apparent “edge-triggered” behaviour is just the result of comparing sampled levels.

Important implication (our actual problem)

Because no real edge detection is implemented:

Short pulses can be missed, depending on the sampling and debounce timing.
In other words: a signal must remain active for a certain minimum duration to be recognized — but the required duration is not documented.
This also requires reconfiguration before entering Hibernate, otherwise the wake-up condition may not match the actual signal state at the moment of entering Hibernate.

This behaviour is critical for system design and should be reflected in the documentation.

Request

Given these findings, the current datasheet wording (“edge-triggered wake-up”) is misleading and suggests true edge/event detection, which is not the case.
To prevent misinterpretation and debugging issues, could you please update or clarify the documentation to explicitly state:

that SHPHLD wake-up is level-triggered due to synchronization and debounce
that short pulses may be lost
that minimum pulse width requirements apply
and that a fresh configuration may (in some certain cases) be required before entering Hibernate

Thanks again for your support and for considering these corrections.

Best regards,
Philipp

RE: Unexpected Wakeup from Hibernate Mode via SHPHLD with Rising-Edge Configuration on nPM2100

Kazi Afroza Sultana — Thu, 04 Dec 2025 11:40:17 GMT

Hello,

I have some feedback from team. we managed to simulate the scenario.

Cycling between entry and wakeup from hibernate should work after first configuration. We also have checked that hibernatePT which requires reconfiguration everytime after wakeup (it will reload OTP values).

Wakeup event supposed to be edge or level-triggered? SHPHLD pin is synced and debounce filtered, so it is more like level active. If it was already in wakeup condition and then it is not seen any edges, but if it is not in wake-up condition then you might call it edge triggered.

RE: Unexpected Wakeup from Hibernate Mode via SHPHLD with Rising-Edge Configuration on nPM2100

vielleicht — Fri, 28 Nov 2025 11:44:57 GMT

Sorry, I misspelled the correct register. Obviously it is 0xC1. But still, I think it is not "edge" detection, like you mentioned, but more like level detection. That's why I had to implement a work around.

RE: Unexpected Wakeup from Hibernate Mode via SHPHLD with Rising-Edge Configuration on nPM2100

Kazi Afroza Sultana — Tue, 25 Nov 2025 11:56:24 GMT

Hello,

We have few more observation from your first thread.

a. The vibration sensor is usually closed, pulling SHPHLD to GND (low) during rest. Is the sensor output glitchy? Will it require debounce filtering?

b. The PMIC is configured to wake on a Rising Edge on SHPHLD (via register 0xC2 = 1) Correct register address 0xC1

Register 0xC2 (SHPHLD) instead configures the pull‑up / pull‑down and weak pull‑up current on the SHPHLD pin (RESISTOR, CURR, PULL fields). It does not select the edge.[SHPHLD reg]

So, to wake on rising edge on SHPHLD you must set EDGE = Rising (1) in 0xC1, and then use 0xC2 only to set the desired pull configuration

RE: Unexpected Wakeup from Hibernate Mode via SHPHLD with Rising-Edge Configuration on nPM2100

vielleicht — Wed, 19 Nov 2025 10:07:38 GMT

Hi. Is there any new information to this? Documentation still uses the edge terminology for wake-up configuration: WAKEUP.

RE: Unexpected Wakeup from Hibernate Mode via SHPHLD with Rising-Edge Configuration on nPM2100

Kazi Afroza Sultana — Wed, 23 Jul 2025 11:06:48 GMT

Hello,

I have got some reply from team. After testing the same way developer found both rising and falling edge behave same. If the SHPHLD pin is already in the active state (low for falling/ high for rising), the wakeup happens immediately.

We don't think that the SHPHLD behavior can be considered edge triggered in any situation, the Product documentation is misleading using the "edge" terminology, we think it should be regarded as level-triggered at all times / in any configuration

I would like to provide few more information later.

RE: Unexpected Wakeup from Hibernate Mode via SHPHLD with Rising-Edge Configuration on nPM2100

Kazi Afroza Sultana — Thu, 17 Jul 2025 08:26:10 GMT

Hello,

Thanks for sharing details to us.

I have not found any workaround or register sequence for initializing the edge detection logic between Hybernate Cycle. I have asked team to check if this is a bug. I will come back to you soon.

It's summer vacation time here. Please accept apology if there is a bit delayed response.

Thanks.

Kazi

RE: Unexpected Wakeup from Hibernate Mode via SHPHLD with Rising-Edge Configuration on nPM2100

vielleicht — Wed, 16 Jul 2025 09:15:01 GMT

Additional finding:

After further testing, I noticed that the very first entry into Hibernate after a cold start behaves as expected – edge detection on SHPHLD works reliably (tested multiple times).

However, if the PMIC wakes from Hibernate via SHPHLD and I put the system back into Hibernate mode (without cold reset), then:

- The system immediately wakes again via SHPHLD, even though the SHPHLD pin remains stable (physical switch attached).
- This suggests that SHPHLD edge detection logic may not reinitialize correctly after a prior SHPHLD-based wake event or I'm missing the spot.

This points to a potential issue with edge detection state retention or misbehavior in the internal logic between Hibernate transitions. It seems that the first Hibernate cycle works correctly, but subsequent cycles behave as if the previous wake source is "stuck".

I'm happy to provide register dumps or reinitialization sequences if needed.

Would appreciate clarification if this is known/expected, or if a specific sequence is required to fully reset the SHPHLD wake logic.