uni vs bi directional ESD protection

Electro nS said:

what does unidirectional differ from bidirectional ESD protection which one do you need ??

i am searching for ICs that implement EMI/ESD protection (price is not an issue ,but reliability is ) but i am confused in the rating of positive and negative ESD protection for example

datasheet 1 for NUF2230XV6 : specifies in page 2 top at absolute maximum ratings 15kv (without signs)

datasheet 2 for TPD6F002 : specifies in page 2 buttom at esd protection ratings +/-15kv

are these numbers tha same , because IF you look at the schematic (diagram) of both you will find it the same :

i cannot understand the rating in datasheet 2 , how is it able to clamp the negative spikes ???

please explain to me , i am LOST

Click to expand...

crutschow said:

The negative spike is clamped by the zener conducting in its forward direction (where it acts as a normal diode). You need both positive and negative voltage protection because the ESD source can have either polarity.

Click to expand...

schmitt trigger said:

The TI spec sheet has a plot (figure 1) which indicates that indeed, there are 6 volt zeners inside the device as shown in the schematic.

Now, the spec sheet also indicate that the device is capable of suppressing:

– ± 15-kV Human-Body Model (HBM)
– ± 20-kV IEC 61000-4-2 Contact Discharge
– ± 30-kV IEC 61000-4-2 Air-Gap Discharge

The important distinction here, is the energy content of each pulse depends not only on the voltage value, but in the capacitance and series impedance of each model. The manufacturer has determined that energy -as defined by each standard- can be safely dissipated, whether negative or positive polarity.

Click to expand...