How to measure power on the STM32N6

EBowdach · ‎2025-07-14

Summary

This article provides a comprehensive guide to measuring power consumption on STM32N6 Nucleo and Discovery boards. It covers the STM32N6's multiple power supply domains and explains their impact on power usage. You learn how to identify measurement points and modify the boards for accurate current sensing. Additionally, using tools such as digital multimeters or the STLINK-V3PWR with STM32CubeMonitor-PWR software for precise power profiling.

Essential prerequisites, detailed step-by-step instructions, and important tips ensure you can confidently optimize your design's energy efficiency. For deeper technical details, refer to the included documentation and support resources.

Introduction

The STM32N6 microcontroller features multiple power supply domains, each serving a specific purpose in the system's operation. The main power supplies are marked in bold:

Name	Typical or Range	Description
VDD	1.8 V / 3.3 V	Power supply for most I/Os
VDDIO2/3/4/5	1.8 V / 3.3 V	Independent power supply for I/Os related to SDMMC1, SDMMC2, XSPIM1, and XSPIM2
VDDA18AON	1.8 V	Analog power supply for system analog such as reset, power management, oscillators, and OTP
VDDCORE	0.81 V (0.89 V overdrive)	Digital power supply for Core Cortex®-M55 domain. Overdrive available to get higher CPU frequency
VDDSMPS, VLXSMPS, VFBSMPS, VSSSMPS		Step-down converter, SMPS connected
VDDCSI	0.81 V (0.89 V overdrive)	Power supply for CSI PHY digital supply input, usually connected to VDDCORE
VDDA18PLL	1.8 V	Analog power supply for RCC PLLs
VDDA18CSI, VDDA18USB	1.8 V	Analog power supply for various PHY
VDDA18ADC	1.8 V	Analog power supply for ADCs and VREFBUF
Vref+ , Vref-	Max VDDA18ADC	external reference voltage for ADCs, independent from any other supply
PDR_ON	1.8 V	Power-down reset enable
VDDA18PMU	1.8 V	Analog power supply for the SMPS step-down converter
VDD33USB	3.3 V	Power supply input for respectively USB PHY and USB Type-C® power delivery PHY and related I/Os
VBAT	1.62 – 3.6 V	Backup supply, usually connected to a 3V coin-cell battery
Internally generated power supplies
V08CAP	0.8 V	Regulator decoupling for backup domain and Smart Run Domain. Internally supplied by either VDD or VBAT

The block diagram (from RM0486) below illustrates the power supply architecture and how the domains connect internally and externally.

Understanding power consumption is critical for developers, especially in energy-sensitive applications. The first step is to familiarize yourself with the power supply architecture and its correlation with your design. Two key factors significantly impact power consumption:

Voltage: Higher voltages increase power consumption for the same current.
CPU Frequency: Faster clock speeds consume more power.

For example, the VDDCore can be set to overdrive mode to boost performance. While this increases voltage and power consumption, it allows the MCU to operate at higher frequencies.

1. Measuring power consumption on Nucleo and Discovery boards

The Nucleo and Discovery boards for STM32N6 are configured with a VDD domain set to 3.3 V. Keep in mind that the datasheet provides current consumption values for VDD = 1.8 V. This means that the power measurements you perform on the boards will not directly correlate with the datasheet values, as the higher VDD voltage (3.3 V) results in increased power consumption.

By default, the Nucleo and Discovery boards are designed for general use, but with simple modifications, they can be configured to measure power consumption. To measure power on the various power rails, you need to modify the boards. This guide walks you through the steps required to perform these modifications and accurately measure power consumption.

2. Prerequisites

Before you begin measuring power on the STM32N6 Nucleo and Discovery boards, ensure you have the following tools and documentation ready:

2.1 Tools

Soldering station
- Soldering iron
- Tweezers / forceps
- Solder sucker
- Additional tools for handling small surface-mount parts, such as magnifying tools
Current measurement tool
- STLINK-V3PWR (recommended for accurate power profiling)
- Digital multimeter with shunt resistor (as an alternative)
Jumper wires
USB Type-C® cable
- Two cables if using a STLINK-V3PWR
STM32CubeMonitor-PWR
- Required if you are using STLINK-V3PWR for current measurement

2.2 Documentation

The following documents are essential for understanding the board architecture and performing modifications. Make sure to review them before starting.

STM32N6 Nucleo board
STM32N6 Discovery kit
STM32N6x5xx / STM32N6x7xx datasheet
- Datasheet (DS14791)
STM32N6 reference manual
- Reference manual (RM0486)
STLINK-V3PWR usage guide
- Application note (AN5999)
STM32CubeMonitor-PWR user manual
- User manual (UM2202)
Getting started with hardware development for STM32N6 MCUs
- Application note (AN5967)

3. STM32N6 power supply architecture

Both the Nucleo and Discovery boards share a similar power supply architecture. There are a few additional features on the Discovery board, such as an SD card, MEMS microphone, and extra switches. You can select the power source on each board as follows:

Discovery board: Use the JP2 jumper.
Nucleo board: Use the CN9 jumper.

The available power source options for both boards are:

5V_STLink (powered via the STLINK USB port)
5V_USB_SNK (powered via the USB Type-C® port)
5V_VIN (powered via an external VIN source)

By default, the MCU power supply is configured for an external SMPS. The following power supplies are available on both boards and can be measured:

VDD / VDDIO: External power supply for I/Os
VDDA18AON: External power supply for analog blocks (for example, reset, power management, oscillators, and OTP memory)
VDDSMPS: External power supply for the SMPS step-down converter
VDDAV18: External analog power supplies
VDD33USB: External power supply for USB2 HS PHYs and USB Type-C®
VDDCore: Digital core domain supply

Note: If you are unsure about the differences between these power supplies or how they are connected, refer to the schematic or the hardware development guide for more detailed explanations. These resources provide valuable insights into the board's power supply architecture and its relationship with the MCU.

Additionally, note that the current of the backup domain cannot be measured directly. However, you can find its current consumption in VBAT mode in Table 45 of the datasheet.

4. Identify the measurement points

To measure power, locate the appropriate measurement points on the boards. Refer to the schematic and user manuals for guidance:

Discovery board: Section 7.4.6 of the user manual describes consumption measurement using the CN2 pins (14-pin header).
Nucleo board: Section 7.4.6 of the user manual describes consumption measurement using the CN12 pins (14-pin header).

Use the schematics to understand why certain resistors must be removed to enable power measurements. For example, pins 1 and 2 on the header are connected via a resistor that needs to be removed to insert your measurement tool.

Discovery board measurement points on CN2:

Nucleo board measurement points on CN12:

Nucleo board schematic of CN12

5. Modify the board for measurement

To measure power on the STM32N6 Nucleo or Discovery boards, modify the hardware by removing specific resistors (and capacitors, if using STLINK-V3PWR). Let us walk through an example of how to measure power on pins 1 and 2 of the CN2 (Discovery) and CN12 (Nucleo) connectors.

Discovery board modifications:

Nucleo board modifications:

5.1 Example: measuring power on pins 1 and 2 (external SMPS input current)

Locate the measurement points:

On the Discovery board, pins 1 and 2 of the CN2 connector correspond to the external SMPS input current.
On the Nucleo board, pins 1 and 2 of the CN12 connector serve the same purpose.

Remove the resistor:
- For the Nucleo board, remove R28.
- For the Discovery board, remove R23.

The zero-ohm resistors connect pins 1 and 2. Removing it breaks the circuit, allowing you to measure the voltage drop across the shunt resistor.
Refer to the user manual and schematic to identify these resistors on the physical board.

For STLINK-V3PWR users and digital multimeter in ammeter mode:
- In addition to removing the resistor, you need to remove nearby components.
  - On the Nucleo board, remove C21 and R19.
  - On the Discovery board, remove C27 and R24.

These components are located near the previously removed resistor and are shown in the schematic for reference.

Connect your measurement tool:
- For a digital multimeter:
  - Attach jumper wires to pins 1 and 2 of the CN2 (Discovery) or CN12 (Nucleo) connector.
  - Connect the multimeter probes to the jumper wires. Make sure that the multimeter is set up to measure current (for example, move the red probe to the correct input to measure current and set the knob to DC current).
- For STLINK-V3PWR:
  - Screw jumper wires into the OUT and GND terminals of the STLINK-V3PWR.
  - Connect the jumper wires to pins 2 (OUT) and 8 (GND) of the CN2 (Discovery) or CN12 (Nucleo) connector.
Power the board

Use a USB Type-C® cable to connect the Nucleo or Discovery board to a power source (for example, a computer).

6. Perform the measurement

6.1 Digital multimeter

Ensure your multimeter is properly configured and connected to the STM32N6 board as described in the previous section.
Power the board using a USB Type-C® cable (connected to a computer or other power source).
Observe the current value displayed on the multimeter.

6.2 STLINK-V3PWR with STM32CubeMonitor-PWR

Connect the hardware

Attach jumper wires to the OUT and GND terminals of the STLINK-V3PWR and
Use a USB Type-C® cable to power the STLINK-V3PWR and the board.

Launch STM32CubeMonitor-PWR

Open the software and select the STLINK-V3PWR from the SELECT BOARD dropdown (for example, "STLinkV3PWR @ COMX").
Click TAKE CONTROL to establish communication.

Adjust settings (optional)

Increase the current threshold (for example, to 50,000 µA) in the "Settings" menu to avoid errors during measurement.

Start the acquisition

Click START ACQUISITION to begin recording current measurements.
Monitor the real-time current graph and numerical values on the dashboard.

Save the data (optional):

Use the save or export option to save your measurement data for analysis.

7. Repeat for other power supplies

For other power rails, follow the same process:

Remove one or more relevant resistors (and capacitors if using STLINK-V3PWR). Refer to the consumption measurement section of the board user manual.
Connect jumper wires to the appropriate pins on CN2 (Discovery) or CN12 (Nucleo).
Do the measurement using the steps above.

8. Important notes

Ensure that your workspace is free of potential sources of electrostatic discharge (ESD) to avoid damaging the boards.
Be precise when handling jumper wires and ensure they do not touch each other during measurement.
If you encounter errors in STM32CubeMonitor-PWR, double-check the hardware connections and ensure that the current threshold is set appropriately.
We also have a guide for measuring power consumption on the N6 boards with AI running. Feel free to refer to it if you are interested!

Conclusion

Accurately measuring power consumption on the STM32N6 Nucleo and Discovery boards is critical for optimizing energy efficiency and validating design performance. This guide has provided a detailed walkthrough of the power supply architecture, board modifications, and measurement techniques using tools like a digital multimeter or STLINK-V3PWR.

For further details on the power supply domains or schematic connections, refer to the user manuals, datasheets, or schematics. These resources are invaluable for understanding the nuances of the board's design and ensuring accurate measurements.

If you encounter issues or require additional support, consult our knowledge base or reach out to our technical support team using this link. We hope this guide helps streamline your development process and enables you to achieve your design goals efficiently.