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Monday, September 7th 2009, 11:16pm

GPRS powered over USB (Peak current 2A)

Q: Type of module? A:GC864 PY (or similar)
Q: Firmware version? A: no idea
Q: Type of starter kit you have? none
(S1, S1B, S2, S3, S4, EVK1, EVK2, none, other)


I'm thinking about building a GPRS device that is connected and supplied via USB. My favorite GPRS module is the GC864 PY.
The USB port is able to deliver a steady current of 500mA at a maximum.
Now, I've read that the GPRS modules are taking up to 2A peak current. Is there any proven solution that allows using GPRS modules with a 500mA source?

Best regards,

P.S: I want to appologize in advance if there's already a FAQ regarding that topic or if I posted in wrong Forum!


Tuesday, September 8th 2009, 8:37am

RE: GPRS powered over USB (Peak current 2A)

an interesting thought to supply a module via USB. I don't know is the voltage from there >5,5VDC? In any case you need power supply which is sufficient for a peek current from 2.5A (depends from GSM receive level). You should test it with a buffer battery which is charged from USB.
With our starter kit S3 / GC864 and battery (and a converter USB=>RS232) you have all what you need for a test. Have a look here
and don't hesitate asking for a special offer.




Tuesday, September 8th 2009, 3:57pm

RE: GPRS powered over USB (Peak current 2A)

Can you believe that a 7805 + 2 diodes in row + a low ESR capacitors will do the job? It is not the professional version. :-)

Please order just order an starter kit with S3 board. With the kit you will get some USB to CMOS cables too. If then wire the 5 Volt of USB to the Micrel regulator on S3 board and replace the capacitors to low ESR capacitors then you have a working sample. Next step is then to redesign it to your PCB.

Last not least you can place an order with us and one of our value added partners will develop you a customised demo PCB up to a final product.




Wednesday, September 23rd 2009, 1:36pm

Question by email to me. I post it here, because it is close the same:

Q: I have tested the GE865-quad and the GPS-receiver (with larger antenna) with very VERY good results.
Unfortunately, we have no room for the GSM antenna that you kindly sent and around construction.
Instead we are testing a patch antenna for 900/1800 with good result.

A: Any GSM patch antenna will interfere with the PCB. It will loose its 50 Ohm impedance. BTW, a piece of wire could be an antenna as well. It will not be that perfect, but ir will work. A non customised GSM patch antena will give a result between a piece of wire and the embedded GSM antenna ANT-GXE474 listed here:
More about antenna design here:…he-Key-2009.pdf

Q: As we intend to use the battery LIPO 450 mAh to GPS receiver and GE865 modem I just like to hear your opinion for such usage.
I saw i the data of the LiIon battery (LIPO 450mHa) that the maximum discharge current was less that 2A.
Perhaps we have to step up to the next larger battery that will have a discharge current of 1850 mAh?
A: As told before, some good low ESR capacitors will be helpful for the LIPO 450 mAh.

Q:I understand that the battery must be able to supply at least 2A in peek. Do you know if the 450mAh version will.
A: It is less, please have a look on the data sheet listed here:

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