Powering SIM800


#1

Dear Sir, I have mentioned my problems below Please reply me soon in easy description as I am from Software background and have sound knowledge of circuits.

Dear Sir, I have bought this module,
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And want to power it with 3.7v lipo battery. But in the Datasheet, I have some problems to discuss with you. I am attaching two snapshots from the datasheet below.
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Issues :

  1. There is not any voltage rating of the capacitors CA , CB , 33PF , 10PF in the datasheet. So what would be the voltage rating of these 4 capacitors to choose ?
  2. According to the first snapshot , which one is the correct power ciruit shown below ?
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  3. Datasheet shows CA is Tantalam capacitor. Can i use a non SMD capacitor (eg. An electrolytic capacitor) at the place of Tantalam capacitor.
  4. Is VBAT pin is Vcc pin, here ?
  5. Second snapshot states that -
    “Total impedence between battery and VBAT pins shoud be less than 150mOhm”
    Sir, does this power circuit follows this statement or this statement is not of much importance.

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#2

The capacitor voltage rating can be anything >6.3V since the largest voltage they encounter is 4.2V because of LiPo battery.

Both will work. You don’t need those capacitors when you are using a LiPo. Capacitors are useful when using with Noisy and low current sources.

Yes you can use Electrolytic capacitor.

Yes, In SIMCOM modules VBATT pins are the main power source pins.

Not important. LiPo powered circuits work great. But use atleast >500mAh capacity batteries.


#3

Why does the zener voltage has to be 5.1, when the max workable voltage of sim is 4.2v?


#4

Because 5.1V zener starts conducting before the voltage reaches 5.1V. if you use 4.2V diode, it will start conducting before it reaches 4.2V. Which is a waste .