B.2.3. Power sequencing

There is an internal parasitic diode path from core voltage to I/O voltage. If the lower core voltage is powered up earlier than the higher I/O voltage, current flow through the parasitic diode can cause latchup.

To prevent latchup, ensure that the higher I/O voltage is powered on before the core voltage.

Caution

If you cannot ensure that the I/O voltage is always higher than the core voltage, use a low-voltage drop Schottcky diode between the two supplies (anode to VDDC and cathode to VDDIO).

Copyright © 2004, 2006 ARM Limited. All rights reserved.ARM DDI 0287B
Non-Confidential