Important intuitive point - TVS does not have sharp breakdown like a zener.
Note, carefully Bordodynov's specs. Breakdown (probably at 10-100mA) of 26.7V to 29.5V. Conduction voltage rises 9V by the time the conduction current rises to 15.4A. Of course, no ordinary zener can handle that sort of current.
Jim Wagner
Oregon Research Electronics
On Jul 9, 2013, at 11:03 PM, §¡§Ý§Ö§Ü§ã§Ñ§ß§Õ§â §¢§à§â§Õ§à§Õ§í§ß§à§Ó wrote:
All you get it right. Carefully study the documentation for the complete set.
Datasheet ---->
Breakdown Voltage Vbr=26.7- 29.5V,
Clamping Voltage Vc=38.9V at IPPM=15.4A
Bordodynov.
10.07.2013, 09:46, "eqmqiq" <g9512728@...>:
Thanks for everyone's suggestion, I put a new TVS from the LTspice library(SMBJ24CA) and set a series resistance(0.5 ohm) for the voltage source.
the simulation result shows the voltage is clamped at 36V, but the breakdown voltage of the TVS is 24V, I don't understand why...? wrong parameter setting??
I update the asc file to TEMP folder with the same file name " TVS_clamp.asc"
--- In LTspice@..., Andy <Andrew.Ingraham@...> wrote:
Everything said here is correct. The voltage source has precisely zero
output resistance, so it will sustain the driven voltage at whatever
current, no matter how hard the TVS tries to shunt it.
However, the other thing I find noteworthy is that your TVS is conducting
hundreds of amps even with the normal operating voltage (12.8V) when there
is no spike. I do not think you have set up its model parameters
correctly. Despite the fact that you have a TVS schematic symbol, the
parameters you gave it are for an ordinary silicon diode.
LTspice comes with two TVS diodes in its standard diode library. They use
different parameters than the ones you've specified.
Regards,
Andy
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