Migration from EP4CE115 to EP4CE75, package F484

[Altera_Forum]

Hello everybody, 

 does anybody have experiences about migration from Cyclone IV EP4CE115 to EP4CE75 with the package F484? The reason is the cost: The "75" is roughly half price of the "115".  Background: We made a board for EP4CE115. For one application we actually don't need so many LEs. A EP4CE40 would be enough, but EP4CE75 is easier for migration.  We don't use any differential singals or IOs with reference voltages. Therefore, for us, the difference between "75" and "115" is quite simple: Six IOs in "75" are GND in "115" and another six IOs in "75" are VccINT in "115". Principally I could actually directly put an "75" on the footprint of a "115". These 12 IO pins will be connected with either GND or VCCINT (1.2V).   If I set these 12 pins as tristated, I know there would be no problem for the pins connecting GND. But for the pins connecting VCCINT, I am not quite sure. I have VCCIO = 3.0 V. The 1.2 V VccINT is right at the middle point between high and low levels. Although the pin would be tristated, I am afraid there might be some current flowing on these pins at least because of the internal pull-up resistances.   Will this cause any problems? Does anybody have experiences of such migration? P.S. We are using this board for an industrial application (motor control)?  Thank you in advance!  Michael

[Altera_Forum]

All you have to do is enable migration compatibility between both parts in Quartus device settings and connect the unused pins as suggested in the pinout file.

[Altera_Forum]

Thank you, FvM! This is a cool feature. Good to know! 

 In between we also tested it. If supplied with 1.2V to a tri-state input pin with weak pull-up, we measured a current of 0.095 mA. If this pin is set as tri-state input without pull-up, no current (<1 uA)) was measured with a normal multimeter. VccIO = 3.0V. If this pin is connected directly with GND, the currents were 0.01 mA and 0.00 mA for both conditions, respectively.   Michael