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

[Muhammed]

Hi Einar,

Thanks for the quick response.

I have used the sample application provided Nordic SDK v3.0.0 which is "Bluetooh Direct Advertising". In this code i have modified the advertising interval and packet length only. In the non advertising time the system is going to sleep mode as per the code. Please find code snippet below.

• Is there any other peripheral running in this example code? I didn't enabled anything apart from the above two modifications. 
• The spike in 1Hz is expected, That is advertising spikes. However we are worried about the spikes (~2mA) in between the adv interval. The first plot which i shared in the first post is the zoomed-in view of the spikes of in between the adv interval. 
• Disabled the UART as you suggested, Current reduced 
  • Added CONFIG_SERIAL=n in the project configuration.
• However after this configuration we got a big spike (~30mA) before the all advertisement. Please find the scope image below.
  
  
  This spike occurs before all advertisement. Is it because of wakeup from the sleep? If not how to eliminate it?

Thanks,

Muhammed