1889 - MachXO2: I want to use the output of one Lattice MachXO2 I/O bank to control power on the board to the remaining VCCIO banks. Is this possible assuming that I will first power up the MachXO2 using only the VCC core and one
The user can power up the Lattice MachXO2 part using only the VCC core and one VCCIO bank. There are, however, a few constraints:
- As per the "Typical I/O Behavior During Power-up" section of the MachXO2 Family Data Sheet, the user needs to pick VCCIO0 as the one I/O bank to initially power up. Otherwise, the device will remain in a power-on reset state.
- As the user manages to power-up the remaining banks, the user needs to make sure critical control signals are not glitching as a result. For example, assign the global reset input signal to VCCIO0 to avoid any glitches on this signal when other VCCIO banks are powered up.
- MachXO2 Family Data Sheet recommends tying power supplies together as per the first note under the "Recommended Operating Conditions" table. The recommendation is to ensure leakage current does not occur between supplies that are configured to the same voltage. Since the user will be turning on VCCIO banks independently, there will be small voltage differences between the VCCIO banks that are configured to the same voltage level. As a result, some leakage current will drain between these bank supplies. This will result in an overall higher standby power than the 19 μW advertised in the MachXO2 Family Data Sheet.