Unexpected Current Spike Between Advertising Events in Direct Advertising Sample (nRF54L15)

[Muhammed]

Hello Nordic Support Team,

I am working with the nRF54L15-DK and testing the Bluetooth Direct Advertising sample application (based on Zephyr). I am measuring current consumption using a DC Power Analyzer.

Observation:

During BLE advertising at a 1000 ms interval, I observe unexpected periodic current spikes between the advertising events.

Spike Details:

• Peak Current: ~1.98 mA

• Duration: ~51.2 µs

• Average: ~0.71 mA

• Interval: Occurs consistently between each advertising event

Expectation:

From the code and system behavior, it appears that the device should be entering sleep mode between advertising intervals. Therefore, I was expecting minimal background activity and a flat low-current line during the advertising gap.

Query:

1. What is causing this periodic current spike?

2. Is it related to any background system task, RAM retention, clock calibration, or BLE stack behavior?

3. How can we suppress or eliminate these spikes to optimize current between advertising events?

Please let me know if I should disable or reconfigure any Zephyr settings or peripherals to minimize this background power consumption.

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Environment:

• SDK: nRF Connect SDK v3.0.0

• Board: nRF54L15-DK

• Sample Used:  Bluetooth Direct Advertising

• Advertising Interval: 1000 ms

• Measurement Tool: DC Power Analyzer 

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Attached the scope images:

• Periodic Current spike 
  
  
  
• 1s interval current
  

Let me know if you need any additional traces, logs, or oscilloscope captures. Looking forward to your insights.

Best regards,
Muhammed

[Einar Thorsrud]

Hi Muhammed,

What is causing this periodic current spike?

The spikes I see at 1 Hz is expected given that that is the advertising interval, so the spikes are expected.

Is it related to any background system task, RAM retention, clock calibration, or BLE stack behavior?

I assuem the problem here is the high idle current (the current consumtpion between the spikes caused by advertising)? This looks like more ocnstant curernt consuption (though you wil see high frequency spikes due to DC/DC operation). 

How can we suppress or eliminate these spikes to optimize current between advertising events?

Disable any peripherals or resources that is not needed durign sleep, paritcularily any that requier the high frequech clock, such as UART or other serial interraces. There are some typicall reason for high current consumption, and often it is caused by UART logging. Do you have UART enabled? If so, you should disable it. See Power optimization recommendations. If that does not help, we need to look a bit further, and would need more information about your application.

PS: I suspect that some information may have been lost through processing of AI. If so, please post the original question without AI processing and further replies without AI as it is difficult to know which information is correct and what is AI hallucination.