[SOLVED] TVS to protect PMOS gate: where's better to put it ?

[Lucast85]

Hello,

I've a doubt about positioning TVS to protect a mosfet from ESD's and other over-voltages.
The application is no critical regard switching time so I place a 120Ω resistor in series with gate to reduce gate current during switching.
I think it's a good idea to place a TVS between gate-resistor and GND (upstream the resistor). Instead some people suggest to place the TVS between mosfet gate and GND (downstream the resistor).
What's your opinion? What's better choice? and why?

Follow my option schematic: TVS upstream the 120Ω resistor.



Thank you!!!

 

[rhnrgn]

it is better to put TVS before resistor. Because your aim to use TVS is to protect Gate from high voltage and resistor will help current flow through TVS.

In addition if you want better protection you can add an X7R 100nf Capacitor in parallel to TVS, between TVS and resistor, this capacitor will filter first affect of voltage rise and help TVS to remove voltage rise correctly.

But dont forget this capacitor will increase closing and opening time of mosfet.

 

[flion]

Hi,I think it is better to place a TVS between mosfet gate and GND (downstream the resistor).
because if a high voltage appear in mosfet gate ，this voltage should be released by 2 lines：mosfet and the resistor。mosget may be destroyed。

 

[snail888]

Hi,i think flion's points is better .Put TVS close to mosfet gate as close as possible.ESD contains two type:conducted and radiated.For conducted ESD,upstream or downstream resistor maybe same function.But for radiated ESD,close to mosfet gate is better.

 

[afeionline]

I think it's better to put TVS between gate and source, see the application note as below：
https://www.semtech.com/images/datasheet/transient_voltage_protection_of_mosfets.pdf