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I've asked OnSemi for more fuse info, but not much has come back. So, the fuses remain the same. They are supposed to be blown at 5V,, I just learned, but we are set up for 3.3V. I had one stubborn fuse in the last test batch. Worst case, we must build a special programmer to briefly drive higher voltage into the VIO of the 4-pin bank whose 16 fuses are being blown. That sounds crazy, I know, but how else to get 5V at 35mA? We could come up with a programmable power supply circuit for common board use that normally outputs 3.3V, but can jump up briefly to 5V for the fuse blow. That would need one I/O pin and be under software control. The blow time is under 1ms.
There are quite a few parts with Vpp pins, (both Flash and OTP) in volume production today. It is just less visible than on the 2764.Brian Fairchild wrote:" cgracey : Worst case, we must build a special programmer to briefly drive higher voltage into the VIO of the 4-pin bank whose 16 fuses are being blown."
How wonderfully last century. I don't think I've used a chip that needed a special voltage to program it since the days of the 2764.