Electronics > FPGA
Planning/design/review for a 6-layer Xilinx Artix-7 board for DIY computer.
miken:
--- Quote from: asmi on February 11, 2023, 10:05:07 pm ---
--- Quote from: miken on February 11, 2023, 08:39:19 pm ---Another option for the HDMI 5V is to use a PTN3381B, which contains a boost regulator.
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We already have 12V, so what's the point to drop lower only to go back higher again?
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If you guys are planning to use a HDMI buffer then it'd be all-in-one. But if not, sure, there are other ways of going about it.
BrianHG:
78L05
nockieboy:
--- Quote from: asmi on February 11, 2023, 07:04:14 pm ---HDMI only requires to supply 50 mA of current, so you can simply use any LDO which can work off 12V rail.
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--- Quote from: BrianHG on February 12, 2023, 12:54:10 am ---78L05
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Yeah, wasn't going to over-engineer that as I'd have little use for a 5V line elsewhere. Size would be my priority in part-selection for an LDO here rather than current output.
--- Quote from: asmi on February 11, 2023, 07:04:14 pm ---In a different world I would've used a PCIE switch (for example, this one) and place both mini-PCIE and a regular PCIE ports such that you can connect both at the same time. But in this current reality these switches are both incredibly expensive and are super-hard to find in stock, so I think we will have to settle for having just a single PCIE port.
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:( The price of a lot of stuff has gone through the roof whilst its availability has gone through the floor. Good old supply 'n' demand I guess. Damn annoying though, especially with FPGA's not being exactly cheap to begin with. That was an amazing find, asmi, when we got those 100T's for that price. I wish I'd re-mortgaged the wife and got a few more! :-DD
I had a look for PCIE switches - I'm probably looking at the wrong ones, admittedly, but they don't seem to be too expensive - a couple of bucks each? If I've found the right chip, it doesn't sound like it would break the bank if it gives me another PCIE socket on the board?
I'm looking at this: PI3PCIE3412AZHEX - £1.87 per IC. Am I missing something or misunderstanding the issue?
--- Quote from: miken on February 12, 2023, 12:18:50 am ---If you guys are planning to use a HDMI buffer then it'd be all-in-one. But if not, sure, there are other ways of going about it.
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I've got a TPD12S521 on the BOM currently, although I haven't looked at the HDMI schematic yet. I need to rip out the PTN3366 that I used for the Cyclone board's HDMI output as the Xilinx can run HDMI directly (though I'm putting some protection in place with the TPD12S521).
I've just taken another look at Mouser (I was unaware that there would be HDMI interface chips that supply the 5V for you!) and found this one - the TPD12S016. Looks like it does the ESD suppression of the one above and also produces a 5V rail current-limited to 50mA. Seems like a more suitable solution to a straight LDO? And it's a single part replacement as opposed to having to add an LDO to existing parts. Anyone have any thoughts on this?
asmi:
--- Quote from: nockieboy on February 12, 2023, 09:01:20 am ---Yeah, wasn't going to over-engineer that as I'd have little use for a 5V line elsewhere. Size would be my priority in part-selection for an LDO here rather than current output.
--- End quote ---
I used AZ1117-5.0 fixed voltage version in my Sparta board, and it seemed to work OK. However for this design I'm thinking about turning board on and off using "enable" pins of all regulators, so the LDO will also need to have an enable pin. Still haven't decided on a part yet, will do some searching on a Mouser once I have some time.
--- Quote from: nockieboy on February 12, 2023, 09:01:20 am ---I had a look for PCIE switches - I'm probably looking at the wrong ones, admittedly, but they don't seem to be too expensive - a couple of bucks each? If I've found the right chip, it doesn't sound like it would break the bank if it gives me another PCIE socket on the board?
I'm looking at this: PI3PCIE3412AZHEX - £1.87 per IC. Am I missing something or misunderstanding the issue?
--- End quote ---
What you are looking at is an analog switch, meaning it only physically switches lanes. What I'm talking about is a PCIE protocol switch, which works like a network switch and routes PCIE packets between it's channels, allowing to use both devices.
--- Quote from: nockieboy on February 12, 2023, 09:01:20 am ---I've got a TPD12S521 on the BOM currently, although I haven't looked at the HDMI schematic yet. I need to rip out the PTN3366 that I used for the Cyclone board's HDMI output as the Xilinx can run HDMI directly (though I'm putting some protection in place with the TPD12S521).
I've just taken another look at Mouser (I was unaware that there would be HDMI interface chips that supply the 5V for you!) and found this one - the TPD12S016. Looks like it does the ESD suppression of the one above and also produces a 5V rail current-limited to 50mA. Seems like a more suitable solution to a straight LDO? And it's a single part replacement as opposed to having to add an LDO to existing parts. Anyone have any thoughts on this?
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TPD12S016 still requires LDO, it only does current limiting. TPD12S521 also contains a current limiter, please see the last page of my schematics for reference: https://github.com/asmi84/kicad-projects/blob/master/S7_Min/S7_Min.pdf
dolbeau:
--- Quote from: nockieboy on February 12, 2023, 09:01:20 am ---I've just taken another look at Mouser (I was unaware that there would be HDMI interface chips that supply the 5V for you!) and found this one - the TPD12S016 (...) Anyone have any thoughts on this?
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That's what I use in the NuBusFPGA, 'inspired' by the QMTech Wukong FPGA board. Routing is not too difficult despite the 'single-pad' design (the 4 differential pairs only hit one set of pads, so those have to be connected both to the FPGA and the connector). Works like a charm, both in the Wukong (using Litex's standard HDMI stuff for 1920x1080@60Hz, 32 bits) from a xc7a100tfgg676 -1 and in the NuBusFPGA (ditto, also tested with another HDMI PHY to get audio support) from a xc7a35tcsg324-1.
It does have a regulated 5V output for HDMI, but it needs a 5V input as well (in addition to the 3V3 core voltage).
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