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Analog I/O - How to do it?

S

Spaceghost

Jan 1, 1970
0
Hi, in my past experience with I/O, it's been digital...the pad was from an
IP provider, and had ESD protection. I'm working in the analog world now,
and am wondering how you are supposed to get the signal into the chip. I
mean, do you just directly wire from the bond pad to say, the input terminal
of your op-amp? I guess I'm trying to figure out if any special I/O or
protection circuitry is needed.

Thanks,
Marc
 
At the very least, you'll need a current limiting resistor.
You may need an anti-aliasing filter depending upon the details of you
signal and sampling rate.
 
J

Jim Thompson

Jan 1, 1970
0
Hi, in my past experience with I/O, it's been digital...the pad was from an
IP provider, and had ESD protection. I'm working in the analog world now,
and am wondering how you are supposed to get the signal into the chip. I
mean, do you just directly wire from the bond pad to say, the input terminal
of your op-amp? I guess I'm trying to figure out if any special I/O or
protection circuitry is needed.

Thanks,
Marc

Pads are pads are pads. Now-a-days pads are **always** specified by
the foundry. About the only choice you have is whether to use a
series-R version or not.

But ESD can be a leakage path. Occasionally I specify no ESD
structure, or tie both diodes to ground when signals are small and
ground-centric.

...Jim Thompson
 
S

Spaceghost

Jan 1, 1970
0
Thanks guys. So far I've run into antenna problems when hooking the wire
directly to the gate. My understanding is that during manufacturing if
there is too much metal relative to the gate poly, there can be enough of a
charge buildup to blow up the gate. To fix this I put some clamping diodes
in. Sounds like I should put a resistor in too.

Marc
 
D

Del Cecchi

Jan 1, 1970
0
Spaceghost said:
Thanks guys. So far I've run into antenna problems when hooking the wire
directly to the gate. My understanding is that during manufacturing if
there is too much metal relative to the gate poly, there can be enough of a
charge buildup to blow up the gate. To fix this I put some clamping diodes
in. Sounds like I should put a resistor in too.

Marc

from

Floating metal shapes (bigger than some minimum size ) that don't connect to
diffusion somewhere are banned in many processes. And a pin connected to a
gate without any ESD protection gonna be damn near impossible to handle
without blowing it up.

del cecchi
 
K

Keith Williams

Jan 1, 1970
0
Floating metal shapes (bigger than some minimum size ) that don't connect to
diffusion somewhere are banned in many processes. And a pin connected to a
gate without any ESD protection gonna be damn near impossible to handle
without blowing it up.

Ah Del, what a party poop! ;-)
 
S

Spaceghost

Jan 1, 1970
0
Too late, I already added some diodes!

Marc
 
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