Sorry, you need to enable JavaScript to visit this website.

Improving the 1 volt supply

Solved
5 posts / 0 new
Mrubinstein's picture
Mrubinstein
Junior(0)
Improving the 1 volt supply

My design has a configurable number of compute engines. When I try to use too many of them I exceed the limits of the 1 volt power supply.

I can load the FPGA, but when the PS commands the start of computation, the 1v supply drops to around 0.6v and, I think, the board resets.

Vivado says:
vccint: 2.419 A
vccbram: 0.013 A
vccpint: 0.819 A

I'd like some help to replace or augment the power supply.
I thought I could use something like the
Murata OKR-T/6-W12-C
http://power.murata.com/en/products/dc-dc-converters/single-output-non-i...

Some questions:
o Is there a better approach to the problem?
o Is this feasible with with fair soldering skills and no microscope?
o Is there a better module that the Murata?
o Do I have to disconnect the original MAX15021?
o If so, what's the best way.
o Will the enable signal be compatible?
o Can you suggest mounting?

Thanks,
Michael

ctammann's picture
ctammann
Moderator(0)
1V supply

Hey Michael,
 
While not ideal, since the MAX15021 is a synchronous device connecting another supply in parallel with it should be ok (as long as it is also a synchronous device).  The two supplies will essentially form an uneven current share. 
The easiest way to do what you want to do would be to get an EVM that you could wire in to the output side of the output inductor L5.  Any EVM would work, here's an example - http://www.ti.com/tool/tps54425evm-608  You could also use a bench supply set to 1V.  The load will draw current from whichever voltage is higher, when it dips, the other supply will provide the power.  Again, this isn't ideal and with a bench supply you want to make sure sinking current won't damage it.
Just be sure the output is set to 1V and if it isn't, modify the circuit so that it is correct.  After that, connect the input side of the EVM to the 12V on ZedBoard and make sure the enable is wired to Vin.  That will make the 1V supply come up right away (which will satisfy sequencing since it must come up first) and will increase the current capacity of that rail.  Ideally you would disable the 1V supply on the MAX15021, but to do so you would need to lift pin 25 on the device and tie it to GND. 
Let me know if that makes sense and if you have any other questions.
Thanks
Chris

Mrubinstein's picture
Mrubinstein
Junior(0)
Module vs eval kit

Thanks for the info. This may be easier than I feared.

I think that a pre-packaged module would be easier to mount. Cheaper too.

Here's one from TI:
PTR08060WVD
http://www.ti.com/product/PTR08060W

Before I start ordering and soldering, I'd really appreciate it if you'd take a look the modules and verify that they should work.

Thanks,
Michael

ctammann's picture
ctammann
Moderator(0)
Hey Michael,

Hey Michael,
I think the module you selected should work fine for you.  One additional step I would take though, remove L5 (1V output inductor), R253 and R254.  Removing these 3 devices will completely disconnect the output stage of the 1V supply on the board from the 1V feed that you will connect your external supply with.  Ideally I'd like to disable channel 2 completely, but because of the device package type I don't know how you'd do that.
Removing those 3 components though will disconnect the switching output as well as the compensation and feedback points from the output.  At that point even if that channel is switching, there will be no current through the device so you shouldn't have any problems.
Thanks
Chris

Mrubinstein's picture
Mrubinstein
Junior(0)
Results

Here are some photos:

The PTR08060WVD module:
https://drive.google.com/open?id=0B-pvRu9lqErFUTVLdUh1Smhzc0k

Mounted (above):
https://drive.google.com/open?id=0B-pvRu9lqErFS0ZBODdVVDJiYk0

Mounted (below):
https://drive.google.com/open?id=0B-pvRu9lqErFd0p2SzdoWFBNRDg

With fan:
https://drive.google.com/open?id=0B-pvRu9lqErFZnhQUkx2STNjSVk

Notes:
o Left the old supply in place.
o Put some tape around the module to avoid contact with the display.
o Used 5v to run the module.
o Fan reduces temp from 85 to 70c.

I happy with the result.

Thanks,
Michael