SIM900 and Li-ion 3.7V power supply

[emaro]

hello,
it is mentionned in the datasheet, page 21 of the GSM/GPRS module SIM900 that it is recommanded to connect a 3.6V li-ion cell battery directly to VBAT pins. Also, the power supply must be able to provide up to 2A. i have a 3.7v/1024mah li-ion nokia battery. first question : can this battery provide sufficent current (2A) ? second question : connecting the battery directly to VBAT pins means it can be done without decoupling capacitors ??
thank you

 

[emaro]

any help please!

 

[tpetar]

For what time duration this battery should give 2A? Battery voltage will fall down under load preasure, and high current cant stay long time.

 

[emaro]

hello tpetar,
it is mentionned "3 VBAT pins are dedicated to connect the supply voltage. The power supply of SIM900 has to be a single voltage source of VBAT= 3.4V...4.5V. It must be able to provide sufficient current in a transmit burst which typically rises to 2A"

 

[tpetar]

hello tpetar,
it is mentionned "3 VBAT pins are dedicated to connect the supply voltage. The power supply of SIM900 has to be a single voltage source of VBAT= 3.4V...4.5V. It must be able to provide sufficient current in a transmit burst which typically rises to 2A"

What is "3 VBAT ?

That battery can supply around 1A and over that for sure, but question is for what time. What is nominal average current of SIM900 ?

You just need to read document they say local bypass capacitor is recommended, 100u low ESR, close as possible to VBAT pin.

Use instructions and recommendations from document. Every manufacturer recommendation is not without reasons.

 

[emaro]

SIM900 has 3 pins for power supply named VBAT.
In page 50 in the datasheet, the average current supply for the GPRS data mode (my use with this module) is up to 440mA. i think it is ok with my nokia battery.
For the capacitors i was not ok because when they talked about the recommanded solution wich is the 3.6 V li-ion batteyr they said it can be connected directly without mentionning the capacitors, for that reason i'm asking this.

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what they mean by "during TX burst" ? sorry english is not my native language

 

[tpetar]

Take battery and use 10R on it, current should be around 400R, measure voltage and current during time. In other words make load test. Also can be helpful if you have battery datasheet with graphs.

"TX burst" - When sending data device need more power for short time.

 

[emaro]

that is clear thank you : )
last question i opened this thread can you answer please ?