Author Topic: Power TE0706 from external 3.3V supply  (Read 183 times)

bastionbooger

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Power TE0706 from external 3.3V supply
« on: January 27, 2021, 04:54:07 AM »
Hi.

would it be a good idea to try and connect an external 3.3VDC power supply to the TE0706.

Reason 1: i have a couple of these boards where the 5V-3.3V (4A) buck converter does no longer work. I would like to provide the regular allowed 4A.

Reason 2: I would like to provide 3.3V / 8A to the SoM instead of the current maximum of 4A.

I would proceed to (in both of the above cases)

(as a reminder: 5VIN refers to the 5V barrel jack connector, VIN refers to the 5V rail that the overvoltage protection chip puts out)

1) cut off the 4A power converter (U1)

2) connect 3.3V to two of the IDC connector pins that are normally designed to provide 3.3V to the connected peripheral

3) Cut out R37 to disable undervoltage detection in U9 and connect the same 3.3V supply to 5VIN, so as to power the 1.8V buck converter U3 (with 3.3V instead of 5V). The reason here is that there are no pin headers for the VIN rail.

4) i do not care about USB, so i would cut out U5 or ignore it.

5) there are no other parts in the schematic that use VIN.

I am not looking for an official endorsement or a guarantee. I would like to know whether there is a chance this can work.

Thanks.

JH

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Re: Power TE0706 from external 3.3V supply
« Reply #1 on: January 27, 2021, 07:01:32 AM »
Hi,
which SOM did you use?
If you really need 8A I think you has 2 problems:
1. max current rating over connector pins would be for VIN ~6-7A: -->  2A for 2 adjacent pins and there are 7 Pins for VIN(Module VIN) power supply
https://wiki.trenz-electronic.de/display/PD/4+x+5+SoM+LSHM+B2B+Connectors
https://wiki.trenz-electronic.de/display/PD/4+x+5+SoM+Integration+Guide
2.Cooling solution for SOM: 4x5 modules are very small, so most of the waste heat has to go through coolers. I am not sure if you can get the heat from the module so easily. See also Xilinx package user guide for the corresponding FPGA Family.  Note Xilinx provide power estimator excel sheet also Vivado can estimate power, but you must configure realistic conditions for the some, default setup is too optimistic.


to point 4: Regarding U5 for USB. This is power supply for your connected USB device, which is normally 5V, I don't now what's the minimum power supply, you should check this or cut  U5. So you USB host does not longer work.

to point 5: U5 (EN5331QI) which generate 1.8V for ETH and some SOM bank power will depend on VIN(5V) rail too. From datasheet U5 input range is from 2.4V up to 5.5V.  So you must supply U5 also with your 3.3V

PS: we have the Altium files of the TE0706 online, see download area of the carrier.

br
John






bastionbooger

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Re: Power TE0706 from external 3.3V supply
« Reply #2 on: January 27, 2021, 07:17:56 AM »
the wiki page states: "2.0A per pin (2 adjacent pins powered)". So which is it? 2A per pin or 2A per 2 pins?

I was thinking of TE0741/TE0841 and i know my design can exceed the 24W that the regulators on these modules are able to provide. i can clock down to stay below any upper limit though.

For heat i was thinking of mounting a small fan. That worked with the te0712, but i ended up exceeding the 4A and the buck converter died. Maybe for the te0741 i would end up needing a heatpipe since it would draw about twice of what the te0712 (a200t) draws.

PS: fans and heatpipes are not sold by trenz. Are there compatible third party vendors? I was able to mount one small fan with flexible mounting gear, but it was not a perfect fit.

JH

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Re: Power TE0706 from external 3.3V supply
« Reply #3 on: January 27, 2021, 08:06:10 AM »
Hi,

oh sorry my mistake.

This is from samtec specification:
http://suddendocs.samtec.com/catalog_english/lshm_dv.pdf
"2.0 A per pin
(2 adjacent pins powered)"


So this means appr. 2A per Pin, in case you use 2 pins which are adjacent to each other. If you have a single pin, than it's less

I've checked the older spec version which is available on our wiki attachment
https://wiki.trenz-electronic.de/download/attachments/23625798/lshm_dv.pdf?api=v2
"1.3A per contact
@ 95°C ambient
(6 positions powered)"

So for 4x5 modules and VIN it will be around 9.1(7*1.3A) and 13.3(6*2A+~1.3A). So this should be enough for your purpose.

For cooling solution, you must check temperature of your design. For FPGA, use for example XADC over Vivado HW Manager. This  shows nearly Junction Temp, which Xilinx specified in the DC Switching user guide of the FPGA (depends on temp range you has select). Note, all other components are industrial on the board,and if the heat cannot be dissipated via its cooling solution, then it can happen that these also overheat. See also package user guide of the 7 Series and U Scale Series.

For TE0741 we provide a heat sink:
https://wiki.trenz-electronic.de/display/PD/Cooling+Solutions

You can also use BGA Heat sink and additional fan.

But in any case, you must still check if this is suitable for your running design.

br
John






bastionbooger

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Re: Power TE0706 from external 3.3V supply
« Reply #4 on: January 27, 2021, 08:13:23 AM »
I have XADC monitoring in my design.

I know the standard heat sink will not be sufficient, but what does that mean: "BGA heatsink and additional fan"?

Any specific parts that are recommended for this purpose?

Is the "BGA heatsink" some kind of off-the-shelf standard part?

JH

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Re: Power TE0706 from external 3.3V supply
« Reply #5 on: January 27, 2021, 08:24:54 AM »
Hi,

you must find suitable heatsink which you can glue on the FPGA package, which you used.
Everything depends on your design and the environment where you use the board, so I can't give you a suggestion.

Here are some links
Xilinx
https://www.xilinx.com/support/documentation/user_guides/ug475_7Series_Pkg_Pinout.pdf
chapter 5
https://www.xilinx.com/support/documentation/user_guides/ug575-ultrascale-pkg-pinout.pdf
chapter 10

And search for bga heat sinks on different distributor shop pages, for example:
https://www.mouser.de/Thermal-Management/Heat-Sinks/_/N-5gg0?P=1yzvkztZ1yz8nml

There are also companies which has specialised to develop custom cooling solutions

br
John

bastionbooger

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Re: Power TE0706 from external 3.3V supply
« Reply #6 on: January 27, 2021, 08:36:02 AM »
I can choose a heatsink, but of course it would already help to know which to choose from. Knowing what part has the right distance between the mounting screws and has a suitable profile to fit the FPGA chip surface, ideally without using a pad, but thermal paste.

You mean to say that i should try and find a heatsink that i can glue to the chip? Basically just have to make sure the heatsink surface area is as close to the FPGA surface area as possible.

I looked at a few heatsinks on mouser and most of them have screws. I just take one of those and glue it?

JH

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Re: Power TE0706 from external 3.3V supply
« Reply #7 on: January 27, 2021, 01:08:10 PM »
thermal glue and thermal paste for BGA heat sinks. In this case you has only a cooling solution for the FPGA. In case you use more thermal paste instead of glue, you can remove heat sink also, sometimes there are also some available which can be be mechanically attached to the FPGA. I can't recommend some for these FPGAs on these carriers sorry.
br
John

bastionbooger

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Re: Power TE0706 from external 3.3V supply
« Reply #8 on: January 27, 2021, 01:22:19 PM »
ok, thanks for your help. i appreciate it.

if i go through with it, i will let you know how it went.

cheers.