| Electronics > Projects, Designs, and Technical Stuff |
| supply GSM module with a single cell Lithium battery |
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| alireza7:
hi Dear all I want to design a battery based system which supposed to work for a long time with a single cell 3.6v battery. My GSM module is quectel M66 and works with voltages between 3.3 to 4.2v If I connect the battery directly to the input of the module, after the voltage of battery became bellow 3.3v the module won't work although the battery still has capacity. so the full capacity of the battery will not be used. I want my gsm module still work when the battery voltage is above 2.5V. My idea is using LTC3203 which is a 500mA Output Current Low Noise Dual Mode Step-Up Charge Pumps with 500ma-5v output and then give its output to mic29302 (3A LDO) to get 4v for the gsm module. but I am concerned with output current of LTC3203. peak current of GSM module is 2A. can I handle it by large capacitors at the input of GSM module? Besides my idea do you have any idea? |
| jbb:
I think you will find that the extra run time you get out of the battery between 3.3 and 2.X V may not be worth the trouble of adding a step-up converter. Depending on cell parameters and temperature, you might only get 10% more out of the battery. Also, your proposed step up converter would be quite inefficient. Some cell phones put a supercapacitor in parallel with the battery to support the 2G transmit current pulses. You’ll need quite a bit of capacitance to do that. How about you stick with the basic battery connection and work to reduce the load current of everything else in the system? The Quectel module is 2G. That’s old technology and I haven’t downloaded the data sheet, but I see that the supply current says ‘as low as 1.3mA.’ That’s huge in a battery powered system. Have you looked at the new Cat M1 modules? They are designed for low power low data rate deployments. Finally, a word of caution: if this product is going to be handheld or carried on a belt pouch (or, worst of all, held up to your head), you’ll need to do Specific Absorbtion Rate (SAR) safety testing, which is a giant pain in the ass. If you need that, you should start designing your SAR test right now. I have heard tales of engineers in tears at the test lab when they couldn’t test (and therefore could’t sell) their product. |
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