P6KE TVS diodes maximum frequency

[Em_13]

Hi every one.I want to use TVS diode between drain-source of mosfet to protect it from spark.The switching frequency is 23.4 khz .Can I use these diodes for this freqency?
Let me ask my question in a different way: Are these diodes fast and can be used in 23.4khz or in this frequency has current leakage even in voltage below clamping value ?

 

[KlausST]

Hi

maximum freqyency depend on your circuit, the capacitance of exact type of P6KE you are using
... use the datasheet to find out the P6KE capacitance.

Klaus

 

[Em_13]

There is no mention of capacitance in the datasheet.

 

[KlausST]

Hi,

Post a link to your datasheet.
There should be some information.

Do a pdf search or "cap", "capacit" or similar.

Klaus

 

[Em_13]

Thanks.I search the datasheet and find this:
So how i can find maximum frequency from it?

 

[KlausST]

Hi,

as already mentioned: it depends on your circuit.
Also on how you define "can I use it".
There is no black and white.

Theoretically you may switch huge capacitance, but then you have to expect huge current ... and huge power dissipation. So from the physics there is no limit.

The current is: dV/dt * C
and the power dissipaton is: 0.5 * C * V * V * f

as example:
If your applicaton uses very hard (high dV/dt) switching, the current becomes high, too. Short, but high peaks. Now if your PCB layout is not optimal and there is high stray inductance you get lots of ringing, which may cause lots of EMI and maybe makes the circuit inoperable.

The softer you switch, the more capacitance it can handle.

Idependent of dV/dt there will be power dissipation (mainly in the switching device) just to charge/discharge the capacitor. Since V is quared (in the above formula) it has the highest impact on power dissipation. frequency is given. This the higher the capacitance, the higher the power dissipation.

So if your application is used for high power then maybe your switching devices have 100W of power dissipation. Then an additional of 2W because of the capacitance won´t harm. But if you have a tiny application or 100mW of load power then most certainly you daon´t like to have 3W dissipated just because of the capacitance.

In the end it´s the designer who has to decide whether the "can I use" limit is at
* 1mA, 1A or 25A..
* 10mW, 0.5W or 10W.

As long as you don´t give full application details ... I guess no one can tell you wheter this TVS is useful or not ... one even can not give a recommendation.

Klaus

 

[Easy peasy]

Short answer is yes - but you really need to reveal the max volts, max turn off current and expected duty cycles, e.g. max on time followed by off time - to allow a proper answer from the group.