5411 - Why does iCE40 devices heats up and have high current consumption when VCCIO and VCCIO2 are applied before VCC?

5411 - Why does iCE40 devices heats up and have high current consumption when VCCIO and VCCIO2 are applied before VCC?

If we look at the iCE40 datasheets, we can see that there is a correct Power Supply Sequence for the device to operate properly. VCCIO0 and VCCIO2 should only be applied after Vcc has reached a level of 0.5V or greater. Though the device may functionally work, the device is still not properly configured.

The cause of this could be related to the power-up sequence. One of the reasons the device requires the sequence of power-up is because the device needs to configure/be configured during power-up. The VCC powers up first to allow the internal configuration to be reset and initialized properly. If VCCIO powers up early, it could cause the configuration not to reset to the proper state. When the device is not configured properly, there could be contention in the FPGA logic that can cause DC current. Even if the device appears to be functioning properly to the application, some of the contentions could be an area that is not used in the application, and not observed as a functional failure.

One quick thing for the user to try is to see if he can re-configure the device once he observes this high current state. Since this is SSPI, it has to be done by the external controller, by toggling the CRESETB to re-start configuration.