K21 VOUT33 outputs 5V

[kevinledinh]

Hi NXP team,

I have a question regarding the VOUT33 voltage. I'm using Processor Expert FSL USB CDC component. 

I'm seeing behaviour during initialisation where after the USB module is enabled, the VOUT33 voltage goes from 3.3V to 5V. According to the datasheet, this should not be possible.

The piece of code enabling the module is in usb_dci_kinetis.c, in USB_DCI_Init function:

USB0_CTL = USB_CTL_USBENSOFEN_MASK; /* Enable USB module */

I'm seeing this behaviour on some boards only but this has been causing headaches for production. 

Has anybody encountered this? 

Any help is really appreciated.

Best wishes, Kevin

Update: if a 10k resistor is fitted between VOUT33 and GND, the VOUT33 voltage always stays at 5V when the K21 is powered.

[miduo]

Hi,

What hardware board you used? it is customer board or our evaluation board? For your case, please let me know what you had done with the VREGIN. Does the VREGIN powered between  2.7V to 5.5V?