The general power-up sequence for the TUSB320 device (EN_N tied to ground) is as follows:
- System is powered off (device has no VDD). The TUSB320 device is configured internally in UFP mode with Rds on CC pins (dead battery).
- VDD ramps – POR circuit. VDD must ramp within 25 ms or less.
IO pull-up power rail (for example, pull up on ID, INT, SCL, SDA, ADDR, and
PORT) must ramp with VDD or lag after VDD.
- I2C supply ramps up.
- The TUSB320 device enters
unattached mode and determines the voltage level
from the PORT pin. This determines the mode in
which the TUSB320 device operates
(DFP, UFP, and DRP).
- The TUSB320 device monitors the CC pins as a DFP and VBUS for attach as an UFP.
- The TUSB320 device enters active mode when attach has been successfully detected.