AnsweredAssumed Answered

K21 VOUT33 outputs 5V

Question asked by Phuc Le Dinh on Mar 1, 2017
Latest reply on Mar 10, 2017 by Fang Li

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:


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.