Input Protection for INA116

Hello Colin,

Please understand that there is a difference between ESD and EOS. Here is a link to some videos on the topics:

www.ti.com/precisionlabs

For the INA116, the +/-40V input protection circuitry is there to guard against EOS which thereby protects the ESD structures. It does this by limiting the input current based on the input voltage. Please refer to the "Input Over-Voltage V/I Characteristics" plot on page 5 of the data sheet. As far as what happens outside this range, we neither test nor characterize the device beyond this specification.

Concerning the ESD structures, how they work exactly is proprietary. Some description, however, is discussed in the following post:

e2e.ti.com/.../578825

Typically ESD robustness is a system-level solution and ideally does not depend on the devices' ESD performance themselves, though it sounds like your application is a special case (classroom with carpeted floor). The ESD specifications for devices are mainly there for manufacturing and handling purposes while building a system. I interpret Bruce's comment about "reasonable precautions to minimize ESD" as adding the 10kohm/47pF RC on the input and ensuring that the equipment is handled by people with appropriate ESD protection (e.g. ESD wrist straps, ESD mats on table and/or floor, etc.).

Hope this helps!

Hello Colin,

Your understanding of the ESD diodes and EOS circuit is correct, but I do not recommend placing such large series resistors on the inputs. Perhaps a better approach is to use ferrite beads instead of resistors on the inputs. Ferrite beads have low impedance at low frequency but go to high impedance when presented with a large voltage transient.