Aussie Susan
New Member
I am experimenting with an AD9958 chip that has 56 pins (all underneath the chip!) that I'm attaching to a SchmartBoard prototyping board. At the moment all I've done is to solder the chip to the board - there are no other connections.
Before I started to load the board with the other components, I decided to see if any pof the pins were shorted together by using my DMM and checking adjacent lines.
I have found several pins that show up as short circuits but I can't see any solder bridges etc, even using my 100(+) USB microscope - unless they are underneath the chip itself!!!!!
One thing I have noticed is that the pins that appear to be shorted are all "digital" output pins that are next to a digital VDD (+1.8v) line. Looking at the datasheet it does show the equivlent circuits for the digital I/O pins in question but it does for the +3.3V digital I/O pins and they are 2 FETs in series betwqeen the supply rails with the inputs to their common gates and the outputs from between the 2 FETs.
Assuming something similar as the equivalent circuit for the higher voltage digital ports, I was wondering if it is possible that I'm actually measuring the path through one of the FETs rather than an actual short circuit?
Thanks
Susan
Before I started to load the board with the other components, I decided to see if any pof the pins were shorted together by using my DMM and checking adjacent lines.
I have found several pins that show up as short circuits but I can't see any solder bridges etc, even using my 100(+) USB microscope - unless they are underneath the chip itself!!!!!
One thing I have noticed is that the pins that appear to be shorted are all "digital" output pins that are next to a digital VDD (+1.8v) line. Looking at the datasheet it does show the equivlent circuits for the digital I/O pins in question but it does for the +3.3V digital I/O pins and they are 2 FETs in series betwqeen the supply rails with the inputs to their common gates and the outputs from between the 2 FETs.
Assuming something similar as the equivalent circuit for the higher voltage digital ports, I was wondering if it is possible that I'm actually measuring the path through one of the FETs rather than an actual short circuit?
Thanks
Susan