topic Re: Question about slew rate settings in i.MX Processors

Question about slew rate settings

ko-hey — Fri, 24 Jun 2016 05:37:11 GMT

Hi all

I'm developing a custom board with i.MX6SL and have questions about slew rate.

There are following description in chapter 26.4.2.2 in RM.

http://cache.nxp.com/files/32bit/doc/ref_manual/IMX6SLRM.pdf?fpsp=1&WT_TYPE=Reference%20Manuals&WT_VENDOR=FREESCALE&WT_F…

"Additional 2-bit slew rate control to select between 50, 100, and 200 MHz IO cell operation range with reduced switching noise"

I think that those settings correspond to "SPEED" field in Pad Control Register. Am I correct ?

Those are cutoff frequency. Am I correct ?

If Q1 is correct, both of "SPEED" field and "SRE" field are correspond to slew rate.

What the difference between them ?

There is "SRE" field in Pad Control Register and it have "SLOW" and "FAST" settings.

Are there specific value to each settings ?

Ko-hey

Re: Question about slew rate settings

Yuri — Fri, 24 Jun 2016 06:04:20 GMT

Hello,

Please refer to app note “Influence of Pin Setting on System Function

and Performance”

http://www.nxp.com/files/32bit/doc/app_note/AN5078.pdf

Have a great day,
Yuri

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Re: Question about slew rate settings

ko-hey — Mon, 27 Jun 2016 00:50:35 GMT

Hi Yuri

Thank you for reply.

I understand that there are no specific value for "SLOW" and "FAST" from the document whici you told me.

But there are still some questions.

Could you answer following question ?

Q1-1

This is continuation of Q1.

I found slew rate can calculate a following formula.

(I got from it from http://www.radio-electronics.com/info/circuits/opamp_basics/operational-amplifier-slew-rate.php)

Slew Rate = 2*π*f*V

slew rate is measured in volts / second, although actual measurements are often given in v/µs

f = the highest signal frequency, Hz

V = the maximum peak voltage of the signal.

The freq are correspond to this formula. Is it correct ?

Q1-2

If my understandings of Q1-1 is yes, What the difference between "SRE" and "SPEED" field ?

Both of the settings are correcpond to slew rate. Is there a difference in strength ?

Ko-hey