merapcb wrote:
>
> --- In m..., Joerg wrote:
>> Looks like the battery connection to the RTC isn't locally
>> bypassed. Not sure if required but if the battery hangs off of
>> wires I'd consider it.
>
> Locally bypassed? Meaning? The battery is on a holder on the PCB.
>

Like Emmett wrote, a 0.1uF ceramic right at the battery pins. But you
could ask Maxim if that's needed. My experience is this: Anything that
could form a loop and goes to an IC can damage that IC during a
thunderstorm. And I think you guys in India see a lot of those :-)

>
>> Looks like the problem is not an EEPROM like you said in the first
>> post but with thre realtime clock?
>> Why do you say that? Actually, it is true that I don't know if it is
> with RTC or EEPROM (or both). I assumed EEPROM but it may be RTC. I
> was not fortunate enough to capture that data on debugger (yet).
>

Here is one more suggestion: The I2C traces (where your red arrows are
in the layout) could be moved to the left. That makes them shorter.
Also, there should be a ground trace rounted in parallel with them. That
reduces the loop area.

Besides plain old device malfunction which happens a lot with I2C there
is always a chance that some significant EMI event happens in the field
and induces a spike in such loops. Doesn't have to be a thunderstorm, it
could also be guy next door with his arc welder. Or overhead powerlines
that get switched under load once in a while.

--
Regards, Joerg

http://www.analogconsultants.com/

Start a New Thread

I have seen some part data sheets which describe "high speed mode" which is "compatible" with I2C, and they presecibe smaller resistors (like 1.5K or something). I believe they call is "high speed compatible" because it technically violates some old legacy Philips spec. Anyway, dig into the data sheets and they may give you some suggestions about R sizes based on your Vcc, data speed, etc.

If you're not battery powered, the impact on power will be negligible, but I'm not going to make a blanket statement! Caveat emptor!

Stuart

--- In m..., "merapcb" wrote:
> So you are suggesting that if my application does not care about power (i.e. not battery operated etc) then I lower it? To how much? 2K? 1K?
> --- In m..., "Stuart_Rubin" wrote:
> >
> > In general, lower pull-up resistor values will get you less noise, but higher power consumption. 4K7 doesn't sound too low, though, but it's something to think about.
> >
> > Stuart
>

Start a New Thread