96boards
96Boards-CE-Specification.pdf POWER SUPPLIES specification unclear
Page 19 regarding 1.8V output supply, should be (min 0.1A) ... not "max".
To be honest its rather odd that there is a summary of power available at all (we don't summarize the power available via the 5V line.
Given the text on page 9 ("A minimum of 0.18W to a mezzanine module via the regulated +1.8V line") is unambiguous it might be best just to delete the bracketed text entirely.
Hi Daniel, I'm not sure I agree with the comparison between 1.8 and 5v lines. When you're developing a mezzanine, you can almost (within reason) assume that the 5v line is unlimited, because its probably going to be run off the same VR as the USB ports, so ~1A+, and everybody can build mezzanine boards that draw up to 500 mA (for example) and it will work.
But the 1.8v line is going to be a lot more limited, being sourced from the PMIC. Take for example, you build a mezzanine that draws 50 mA from the 1.8V. If there is a set minimum, we can build mezzanines to work within the minimum available, so 50 < 100, we can generally expect it to work on everything. But without that minimum requirement, what's stopping someone from making an SBC that can only produce 25 mA? Its not necessarily a bad thing that someone does that, but if I'm selling a board that requires 50 mA, and someone wants to use it with that 25 mA board, they'll come after me and say "hey, this thing doesn't work". At least with a minimum printed in the spec, I can say to them that my mezzanine complies with the spec, their SBC does not.
On Mon, Jun 11, 2018 at 07:36:55AM -0700, Adam Serbinski wrote:
Hi Daniel, I'm not sure I agree with the comparison between 1.8 and 5v lines. When you're developing a mezzanine, you can almost (within reason) assume that the 5v line is unlimited, because its probably going to be run off the same VR as the USB ports, so ~1A+, and everybody can build mezzanine boards that draw up to 500 mA (for example) and it will work.
But the 1.8v line is going to be a lot more limited, being sourced from the PMIC. Take for example, you build a mezzanine that draws 50 mA from the 1.8V. If there is a set minimum, we can build mezzanines to work within the minimum available, so 50 < 100, we can generally expect it to work on everything. But without that minimum requirement, what's stopping someone from making an SBC that can only produce 25 mA? Its not necessarily a bad thing that someone does that, but if I'm selling a board that requires 50 mA, and someone wants to use it with that 25 mA board, they'll come after me and say "hey, this thing doesn't work". At least with a minimum printed in the spec, I can say to them that my mezzanine complies with the spec, their SBC does not.
As page 9, the base board is required to provide 0.18W (a.k.a. 0.1A). Similarly all other power limits for the LS connector are documented on page 9.
It is therefore weird that for the I/O voltage reference we express the power limits twice (and also that we use different unit compared to other parts of the doc). It's not that I don't think there should be a minimum it is that we should put in in just one place in the space and remove the easliy misinterpreted duplicated version on page 18.
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Oh, I didn't see that it was written twice. In that case, yeah, its superfluous to have it there at all.
@daniel-thompson Should we get rid off the power supplies section in Page 19?
On Fri, Jul 06, 2018 at 12:06:31AM -0700, Manivannan Sadhasivam wrote:
@daniel-thompson Should we get rid off the power supplies section in Page 19?
Absolutely not!
Just the " (max 0.1A)" in the table, this info is redundant and, as Adam reported, isn't very clear.
Daniel.
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@ASerbinski We are in the processes of launching a new method to receive community input and contribution to the 96Boards specifications. Please hold tight while we put together this plan.
This new method will allow us to host released 96Boards specifications in an open source and version controlled environment with issue tracking. We will be sure to broadcast this through our social channels once there is more information.
I will keep this issue open until the new location is ready, then we can transfer this discussion there.
Thanks!
