Inquiry regarding Power Consumption Optimization in USB Suspend Mode for STM32N657L0

[brenda00]

Hello,

I am currently developing a USB Device application using the STM32N657L0.

I am reaching out to ask for advice because I am having difficulty meeting the target power consumption requirement of 5V, 2mA max during USB Suspend state.

 

Our target conditions and system requirements are as follows:

1. VDDCORE uses an external power supply.
2. The USB Driver must be maintained during USB Suspend.
3. The system must be able to wake up and recover via USB.
4. Power consumption must remain below 5V, 2mA during USB Suspend.

Currently, when the chip is configured in STOP Mode, the measured power consumption is:

1. VDDA18AON (1.8V): ~5mA
2. VDDCORE (0.81V): ~40mA

 

We are looking for ways to further reduce these currents to meet the 2mA requirement.

Could you please guide us on how to optimize the power modes, clock gating, or power supply configurations to achieve this? Any suggestions or reference guidelines would be greatly appreciated.

Thank you for your support.

Best regards,

[FBL]

Hi ​@brenda00 

Can you share schematics? Did you try to reproduce using reference board?

[brenda00]

Hello,

Thank you for your response. Please find our feedback on the items below:

1. We have not yet tested this on the Reference Board(NUCLEO-N657X0-Q).

2. We replaced the STM32N657L0 with the STM32N655L0 and tested it, but observed the same results:

   • VDDA18AON (1.8V): ~5mA

   • VDDCORE (0.81V): ~40mA

3. Please understand that we cannot share the full schematic due to confidentiality. Instead, I have attached key excerpts of the relevant schematic sections.

Please let us know if you need any additional details based on the provided circuit snippets.

Best regards,

[FBL]

Hi ​@brenda00 

USB Suspend is a USB protocol state; Stop mode is an MCU power mode.

USB suspend current limit applies to current the USB function draws from VBUS, not automatically to the sum of current measured on every MCU rail. I assume it is specified in the ECN to USB2.0 specifications, “the suspend current must not be higher than 2.5 mA.”