Transient Voltage Suppressor

[soumen21]

Hi,

Please refer the schematics in attachment. Recently, we found that DB1 and DB7 got shorted. My assumption is that high eft/surge on this lines have made the tvs devices go bad due to tvs not being sufficiently rated. Can you please let me know, if I change the TVS device to a higher energy value, will it pass the test.
Current used TVS part no. is 1SMB12CAT3G and the capacitor used along with the tvs is 08055C103KAT2A. Will this 1SMB12CAT3G tvs sufficient to supress 1.2kV surge.

Regards

 

[chuckey]

0V_F_A has a .001 MF to "earth", but .01 MF to the protected lines. These two values are round the wrong way. If you get a transient on any one line, 45% of it is fed up into all the other lines!!
data sheet : - https://pdf1.alldatasheet.com/datasheet-pdf/view/171122/ONSEMI/1SMB12CAT3G.html Its says good for class 3 >16 KV

Frank

 

[soumen21]

Hi Frank,

Thanks for the reply. The problem that is faced is the TVS and the opamp used. In some cases, the TVS DB101 got shorted and the opamp U9 got electrically damaged. In another case the opamp got electrically damaged and TVS DB1 and DB4 got shorted. Is is maily due the TVS not rated or the grounding used on the board ?

 

[chuckey]

One thing is why DB101 and 107, what is connected to them externally? A low value (resistor (100 ohms?) in series with the lines would limit the inrush current and preserve the TVS
Frank

 

[soumen21]

Well, there are 16 such channels and all are connected indivisuaaly to a transmitter. I assume more eft/surge is experinced on those particular lines on certain event. So, this DB101 and DB107 have gone shorted. This may get repeated in case same case is experienced on the other lines too.

 

[vikash23]

Hi,

Could you pease let me know how the TVS diode can be used on the power supply. Do I need to use it before the fuse or after the fuse.

https://obrazki.elektroda.pl/5560553000_1384770748.jpg

 

[soumen21]

The TVS should be used after fuse.