Q&A: What is POR rise/fall time?

Document created by Yixing Kong Employee on Aug 22, 2013
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Q:

”We noticed that the specified risetime of this signal is max 5nS, while the Sable board schematic shows it driven from open collector/drain using only the 100k haulup provided in the chip. This will have risetimes of 10‘s (if not 100‘s!) of ns.

 

The worrying thing is that the latest datasheet update specifically clarifies this rise time spec, so presumably it‘s considered important. Which is right?

 

If the rise time spec needs to be met, we need a small haul up resistor or an active drive. In that case what rail should be used to haul/drive POR_B high?”

 

It appears to be correct, and what is interesting I checked the PFUZE timing in the datasheet

 

”tr4 Rise time of RESETBMCU - 0.2 ms”

 

Device: i.MX6Q

OS: Linux

Dev Board: i.MX6Q SDB


A:

The 5ns rise/fall time requirement does not apply to i.MX6. This was probably carried over from the i.MX53 where it was required. This will be removed from the datasheet but it will likely not be until the September time frame. We're not doing an update to any of the electrical parameters of the datasheet right now.

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