SMF05C or Zener diode - Which one can i use?

[krishnakumar.r93]

Is the SMF05C connected betwenn SIM CARD and sim900a module really necessary?
Or can i just use 4 ordinary zener diode instead? If yes, what should be the voltage rating of the zener, 3v, 3.3v or 5v?

 

[betwixt]

The SMF05C is just five TVS diodes in one package. They are rated to stand off at 5V. Their purpose is to protect the SIM900a from static charge held on the SIM card as it is inserted. It your SIM is always fitted you don't need the SMF05C, if it can be removed it is advisable although not essential that you use one. You can replace it with five pairs of back to back 4.3V Zeners.

Brian.

 

[D.A.(Tony)Stewart]

SIM cards use sockets, therefore you need 5V TVS which rises to 10V with 10A but < 100pF.

You can't do that with Zeners or power diodes because pF is too high.

SMF05C TVS is mandatory.