How to set USB Regulator to Standby mode?

[joseph0577]

I am wondering how to set the USB voltage regulator to standby mode on the K22FX512VMC chip. We do not need the USB on the project, and would like to save as much power as possible. The reference manual only states that the mode is controlled by 'internal power mode signals'. I use KDS with Processor Expert to program on this project.

[Paul_Tian]

Hi, Gray

In chapter USB controller configuration, you can find a note "When USB is not used in the application, it is recommended that the USB regulator VREGIN and VOUT33 pins remain floating.". There is no need to control any register for this regulator.

Best Regards

Paul

[joseph0577]

Also, while I do not need USB on this project, I may need it in the future, so the regulator is connected to the power supply. When a USB device is not connected to the K22, is it possible to disable the regulator without disconnecting it from the power supply?

[cutworth · Accepted solution]

Hi Gray,

You can disable USB regulator with SIM_SOPT1[USBREGEN] bit.

To allow writing to this bit, you need to write SIM_SOPT1CFG[URWE] bit first.

Hao

[joseph0577]

Thanks!

[joseph0577]

Does the VREGIN pin control whether the regulator is on/off?