[time-nuts] Ebay Huawei Ublox M8T Modules Warning

[ASSI]

Am Samstag, 9. Januar 2021, 23:38:35 CET schrieb gandalfg8 at aol.com:
> Now a question, supposing someone did follow that diagram and applied 5
> Volts to Vcc on the M8T, what is the risk of damage and would it be
> immediately obvious?

The commonly agreed upon definition of an abs max rating is that anything is 
possible if you happen to exceed it even just a tiny bit, including latent or 
immediate permanent damage.  Practically there is always some headroom since 
otherwise nobody would be able to test and guarantee that specification.  How 
much headroom?  You don't know…

Looking at the block diagram that VCC goes into a power management block that 
has a DC/DC converter of unspecified type, but surely some sort of down-
converter, so that VCC terminates into some switching stage and hopefully 
never enters any downstream circuitry directly.  The potential failure modes 
would be direct damage to the switching transistor(s) in the converter due to 
overvoltage or switching loss or (less likely, but possible in certain 
topologies) that the internal supply exceeds whatever voltage it's supposed to 
produce.  Unless the switching stage fails catastrophically (typically 
shorting the supply as a result, which will announce itself immediately) which 
becomes more likely the higher the applied voltage and the longer you apply it 
(both will shorten the lifetime exponentially) I'd suspect that you couldn't 
tell without grinding the chip down and looking at it under an SEM and even 
probing the individual transistors.


Regards,
Achim.
-- 
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