USB-OVP

Andy Green andy at openmoko.com
Fri Aug 29 07:55:03 CEST 2008


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Somebody in the thread at some point said:
| Joerg Reisenweber wrote:
|> Do we really need more reasons to care about that issue?
|
| How about Postel's law ?
|
| http://en.wikipedia.org/wiki/Robustness_Principle
|
| Sounds like a good enough rule to follow at any interface, not just
| software interfaces.

''Be conservative in what you do, be liberal in what you accept from
others'' is a nice general principle.

But then where does one stop, accepting mains power directly, automotive
12V, 12V charger connection, broken chargers...  it is a guiding
principle to be taken into account at specification time.  Every new
thing we accept to support has costs.

What I like though is the "Be conservative in what you do" part of it.
Because we have not seen failures in the field from GTA02 arrangements,
I am having a hard time accepting we need to change anything from proven
GTA02 situation.  If someone can actually show that GTA02 style
arrangement leads to product failure in normal circumstances then it
makes it clear we need to do better.  But it seems thousands of users
are proving it's robust enough already.  Why add reverse voltage
protection when nobody seems to have reversed the voltage on their USB
connector to date?

Still one part of what Joerg has been talking about he characterized as
different component selection so it was more robust, that sounds fine if
it is not adding expense / size.

- -Andy
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