Hi.I have a GPRS product based on an embedded module.
This GPRS module have a power supply with a 4,2V output with a maximum medium of 300~350mA current consumption.
Curently, I am using a power supply based on a LM2596 (fsw = fixed at 150Khz only). Since a all GPRS modules present a high peak current consumption during data transmissions, I think I will need a faster power supply.
I saw the LM2676 have fsw fixed at 260KHz, and I think I will start using it instead of keep using the LM2596 - SMD TO263. I will update the power supply next month and the controller IC is one of the key parts of the power supply.
I was also thinking to use the LM22680 SMD SOIC-8 for this design
Input voltage range is from 10 to 32V only.
Question:Is LM2676 or LM22680 suitable for my project? For GPRS modules?Please give me some other suggestions, if possible.
What is the part numbers of developments boards for these ICs?
Please check the attached PDF. It shows the power supply requirements.
0820.GPRS_power_supply_specs.pdf
http://www.digikey.com/scripts/DKSearch/dksus.dll?Detail&itemSeq=117672525&uq=634795359243376141
http://www.digikey.com/product-detail/en/LM22680MRE-ADJ%2FNOPB/LM22680MRE-ADJCT-ND/1993220
I also would like to know which value range (if there is a standard value) of ferrite beads I could use between the power supply output and the power supply pins of the GPRS module.
Regards.
Help?
Hi Jeferson,
THe LM22680 should work for this design, but because of the high frequency noise spec you will need to be very careful with layout and the output filter componenents.
I asked someone to take a look at this design in more detail, and they should have some more information next week.
Regards,
Marc
Hi.
And how about the LM2676 for this design? It has a fixed switching frequency of 260Khz.
And if I use a LM22680 for the new design, which switching frequency range would be suitable for GPRS? I know it has adjustable frequency, up to 1MHz
Do you know when this person will be able to help me? I want to start updating the hardware soon.
Thanks
Hello Jeferson,
we are working on it and we'll let you know as soon as possible.
Giuseppe
Thanks.
We really need a good solution for this case, because we will update the hardware of a current design, and we have a relative high volume for this product.
If the results with this new hardware be good, we would like to use the same power supply for all of our products based in GPRS/GSM. We are looking for a single solution for all products. We have many many products in development needing this solution.
I have tested the following circuit with the LM22680:
The circuit seems to work fine and it meets the requirements.
The switching frequency is 500kHz.
Please see attached images for ripple constraints.
8738.LM22680.zip
Please let me know if you have any question.
What was the value used for R3?
I have one LM22680EVAL PCB and around 10 ICs samples of LM22680
I have the capacitor below in one of our stock items. I can use it as output capacitor, in parallel with some ceramics.
470uF, 10V, LOW Impedance: http://www.digikey.com/product-detail/en/EEE-FK1A471P/PCE3780TR-ND/765950
I dont want to use the inductor of the EVM, I have 10 samples of each of these:
10uH: http://www.digikey.com/product-detail/en/NR8040T100M/587-2001-2-ND/1739083
22uH: http://www.digikey.com/product-detail/en/NR8040T220M/587-2002-2-ND/1739084
33uH: http://www.digikey.com/product-detail/en/NR8040T330M/587-2636-2-ND/2349965
47uH: http://www.digikey.com/product-detail/en/NR8040T470M/587-2003-2-ND/1739085
I have more than 10 samples of these capacitors, to use at the input, in parallel with some ceramics
INPUT CAPACITORS, ELECTROLYTIC:
330uF, 35V, LOW Impedance: http://www.digikey.com/product-detail/en/EEE-FK1V331AP/PCE4429TR-ND/1141988
470uF, 35V, LOW Impedance: http://www.digikey.com/product-detail/en/EEV-FK1V471Q/PCE3464TR-ND/396276
For D1, I will use a B340A schottky (3A x 40V). It is a stock item.
The input range will be from 10 to 31V only.
R3 is not present on the board, sorry for the misunderstanding. The LM22680 switches at 500kHz by default.
For what concern the inductor i think that 10uH will be enough
Please do not hesitate if you have any problem.
Hi.Thanks for help.Is the LM2676 not suitable for this purpose?
the LM2676 should work fine, i can do some measurements within this week and i will let you know.