SIM800L GND pins

Question

I want to create a PCB design for this . In datasheet of SIM800L i found it has many ground pins. datasheet recommend this :

My first question : is just using 2 , 43 , 44 and 45 pins enough and i should not connect other ground pins to the ground . So leave them unconnected .

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I have SIM800L module but it has not power key .

My second question : if i leave Power Key Unconnected its will start working without problem ? i did not see any power key in module too.

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My third question : according to information above. can i us 3.3v for VSIM ?

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My fourth question : what you think about these 3 capacitors . ( i guess they used for VBAT ) ?

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My fifth question : what is the minimum width for routin line in a PCB specially for this IC ?

Answer 1

1. The four GND pins need special mention as only those pins carry the battery return currents and the other pins don't. It does not mean that other ground pins can be left unconnected. It just means that those pins need widest and shortest path to power source to carry the current.

2. If another board does not have it, chances are you don't either. In some cases it can be used for firmware updating the module, so the question is do you want to support firmware updates or turning the module power on/off with this pin.

3. No you can't. The module gives out supply voltage to SIM and it wants to select the voltage itself. Typically, SIM card voltages include 1.8V and 3.0V, not 3.3V.

4. Yes, most likely the capacitors are for the supply.

5. Whatever you choose. The supply lines need to be wide enough to carry the current. Antenna needs correct impedance. Ground plane is a good idea. Other lines are just digital IO, so you can use smallest width you can.