Forum Discussion
Honored ContributorIm curious why
Noone had any advice about running Cyclone II based boards off rechargeable batteries? Is there something I dont know where it's a bad idea?
25 Replies
Altera_ForumI want you to know I've returned to this project and still intend to finish it. I still appreciate all your good advice, I am now working on getting one of those small text LCDs to work with my project before anything else, then I will return to this problem, thanks for your help.
- Altera_Forum
Thanks (again) Skravats. I actually attended the Arrow event and have the LPRP in hand.
While I have issues with the Arrow event, the LPRP board is pretty cool. Had the LPRP been 1/3 - 1/4th the size, it could have been immediately useful besides just being a dev kit. Hopefully we'll see more battery power dev kits in future. - Altera_Forum
The CellularRam utilized in the LPRP is referenced by the hyperlink below.
It has separate address, data and control busses. It can handle about 135 Mbyte/sec transfer rate and automatically defaults to < 200uW of powerdraw when it is not being accessed. It has both a simple assynchronous (SRAM like) interface or a higher performance burst mode interface. The LPRP uses it in burst mode. http://www.micron.com/products/partdetail?part=mt45w4mw16bcgb-701%20wt (http://www.micron.com/products/partdetail?part=mt45w4mw16bcgb-701%20wt) - Altera_Forum--- Quote Start --- If you want to learn a little more about cyclone devices for battery powered applications, you may want to try to look at this board that linear tech and arrow put together: http://www.fpgajournal.com/articles_2007/20070904_proof.htm this is a nice little write up from fpga journal. good luck, guano --- Quote End --- Thanks for the pointer. Does anymore here happen to know exactly which device is used for the CellularRAM? I'm particularly curious whether they picked a muxed Addr/Data version. Tommy
- Altera_Forum
If you want to go with an easy to use switcher, you can use the point of load modules. One made for FPGA's is the muRata MPDTY01 www.murata.com/power/short/f07e1.pdf . A whole range of options for Altera FPGA's is found at
www.murata.com/power/fpga/altera/index.html including a power supply design reference guild for Altera FPGAs. - Altera_Forum
Buck and boost regulation just refers to whether the output voltage is lower or higher than the input voltage. So a buck regulator is still a switching regulator. For example, you could have a situation where your battery voltage is 3.6V and you have a boost regulator up to 5V and two buck regulators down to 3.3V and 1.2V.
I understand perfectly why you are concerned about getting a more complicated power supply design right first time. I chose to go the linear regulator approach so that I could concentrate on the FPGA operation and not worry if my powers supplies were causing problems. On the production version I might well substitute in switching regulators. You haven't mentioned whether you've looked at Linear Technology's switching regulators yet. I'm sure they are worth considering if you really only have one shot at the overall design. Now, was that Starbucks or Starboosts?:rolleyes: - Altera_Forum
Thanks for info sharky, glad your proj is movin along. I don't see 'switching' in the National Semi page, but i see 'buck', so I will go with that. My concerns are designing and building a complicated PCB and not having it work right after the board house makes it. I really appreciate all the answers, I feel I owe you some Starbucks or something at this point.
- Altera_Forum
Hello again Twinzz
If you're going back to thinking about linear regulators, then the answer is no. All that would do is change where the power is being wasted. e.g. let's say your 1.2V regulator is supplying 100mA. That current is being drawn through the 3.3V regulator and the 5V regulator, adding to their individual dissipation. You've had to drop the same number of volts to get down to 1.2V. There's no getting away from it, linear regulators waste power. If you're thinking of switching regulators, I think a similar argument would apply. I'd try looking for a multi-voltage output device or use separate regulators from a single supply. As a matter of interest, my prototype board is now up and running with linear regulators and they're barely warm. However, my board goes in to a current injection set which could draw 10A from a 230V supply so low power consumption is not an issue. Best regards - Altera_Forum
Looks like the LCD and GPS module are gonna need 5v, if I regulate the battery down to 5v to power those, then regulate that 5v down to 3.3 and 1.2, would that be more efficient that hooking up the regulators in paralell?
- Altera_Forum
Then I will go with the switching ones that you recommend that make for the simplest PCB build.
In case you were wondering why I ask so many questions, I work for Staples now and I gpt my Engineering B.E. 12 years ago, I have no access to peoples or materials of this nature, so I really appreciate all your answers. The national semiconductor page says about buck, buck switching with some complicated PCB setups and transformers they just label as 'custom'. Any suggestions if I can use those?
