dual sim card for mobile module

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ric_vas

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Dual Sim Card

Hi,

I need to interface a second Sim Card to a mobile module (Motorola G20 or Siemens MC35, etc).

These modules only have bus for one sim. I was thinking of having some mux or switch i can control with my uC and connect one or another to the GSM module.

Any idea of device or approach for this?

Thanks,

Ric
 

Dual Sim Card

It really depends on the Sim Card interface. Most either have a chip select, CS, or command, CMD pin. If the card tristates its I/O bus when CS or CMD is inactive, then all the other pins can be paralleled and you only need a mux on the CS or CMD pin.

If you have to isolate every pin, the best option is to use some MOSFET switches. These are available in IC packages with eight or more switches per package. The switches are bi-directional and the delay through the switch is small enough that you should not require any additional logic. For MOSFET switches look at the Maxim or Analog Devices web sites.
 

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