BUF634: TVS selection

Hey Steve,

The max total supply the BUF634 can handle is 36V as you have mentioned. In regards to the abs max of the input, these are whatever your supplies are set as. If you are using the device in a single-supply of 36V then this would be your abs max input.. at a dual supply of +/- 18V, you will not want to exceed either the positive or negative supply so inputting 36V in to the BUF634 will damage the part.

The abs max rating is for the highest voltage in which the device will not be damaged, I would not recommend exceeding this. You may want to add some headroom if possible.

Best,

Hasan Babiker

Whatever supplies you use, there will be about a 2V headroom to those supplies for linear operation, so a TVS 1 V less than the supplies will not turn on in the linear range but will before overdrive to the supplies. Note the BUF634A is the newer version of this. 

Hi Steve,

can you show a schematic?

Kai

Sure, see enclosed - hopefully I did that right....

Note one is for the PCB, other shows connections to the outer enclosure.  Part of the idea is to protect the ICs from damage from a meggar, normally at a 50VDC setting (which should not be done on this box, but has happened).

 Part of the problem I have seen in selecting a TVS is one that has a  reverse standoff or breakdown voltage of 15V has a clamping voltage of about 21V. 

With a supply voltage of 15V, I don’t want the TVS to start conducting.

Thanks for your continued interest in this.

Steve8201 BOB - PCB Schematic.pdf8201 BOB AWM-8x v4.pdf

Hi Steve,

I would give this diode clamp a try:

I prefer using low leakage TVS (e.g. from ST).

Of course, the protection scheme could affect the signal behaviour.

Is the 50V coming from the meggar in some way current limited?

Kai