We are working on a project using K32L2B3x. For this project, the charger we are using does its own D+/D- detection. For the charger to complete the detection properly, it needs to a processor whose D+/D- lines are in a Hi-Z state for the millisecond after power is applied. Is it possible to Hi-Z state the USB data pins (D+/ D-) of K32L2B3x?
It's possible to Hi-Z state the USB data pins (D+/ D-) of K32L2B3x.
I check USB spec. and do experiment on FRDM-K32L2B:
K32L2B USB's DP and DM pin have about 15Kohm pull down resistor, same as USB spec. requirement .
you need to set PDE to 0 to disable pull down resistor. Also, REMEMIDER: VREGIN must be powered. otherwise, there will be leak current.
Let me describe more for easy understanding of NXP.
We are trying to replace competitor's part, and question is asked due to different USB pin spec.
Because competitor MCU(STM32L072RB)'s USB line is multifunctional which can be used GPIO, so it's different with K32L USB.
Reason why Hi-Z of D+/- is to check whether Load Switch is mandatory. With competitor's part, the switch is not.
I think external switch should be used with K32L2B that is different with competitor's MCU. Would you please give feedback for double check?
Below picture is,
- MCU : K32L2B
- The application is using rechargeable battery using USB-C.