AM2431: AM243X MCSPI, UART, GPIO Min/Max Slew rates..

Hi Merril,

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Thanks,

Anshu

Hello  Merril

I am checking with the expert.

The timing is closed at the max rated frequency.

For the above query, are you looking to run the interfaces at max frequency ?

Regards,

Sreenivasa

Hi Sreenivasa,

Thanks!  Their signals are actually slower than the minimum spec.  Looking to understand if this could/would be OK.

Thx, Merril

Hello  Merril

Thank you. 

Newman said:

Their signals are actually slower than the minimum spec

Please eloborate.

Regards,

Sreenivasa

Hi Sreenivasa,

Thx!  For example..

TI Spec: Min Input Slew Rate: 2V/nSec

Actual: Min Input Slew Rate: 1V/nSec

Thx, Merril

Hello  Merril

Thank you. 

Let me check with the device expert.

I suspect customer is not looking to or would want to run at full speed - any thoughts please.

Regards,

Sreenivasa

Hi Sreenivasa,

No, they do not need to run at full speed.

Thx, Merril

Hi Sreenivasa,

Any update?  How can customers be expected to meet these requirements?  Seems kinda impossible to me.  I think these specs must be relaxed.

Thanks, Merril

Hello  Merril

Thank you. 

I checked with the device expert.

The STA team closed the timing for these peripherals at maximum speed and the parameters in the data sheet represent the max speed.

Refer below inputs i received form the device expert:

We do not know how much the slew rate can be relaxed for a specific operating frequency because there are many operating frequency options, and it is not possible to check the slew rate limit for each possible option.

 The only slew rate limits we know are those that apply to the maximum operating frequency.  The customer can operate at any frequency up to the maximum when their system is constrained to operate within our datasheet slew rate limits.  That is the only data points that we have.  We do not know what slew rate limits would apply at any other operating frequency.

Regards,

Sreenivasa

Hi Sreenivasa,

Thanks for the detailed response.  When running at max frequency, could our device be expected to fail w/ "slower than spec'd" inputs.. or has it just not been characterized at these slower rise-times?  ?  What do you recommend the customer do?  They have an external device that is slower than our spec'd minimum.  I think that many customers may have ~similar issue(s) and just have not checked/noticed.  Are you OK to have a call with them to discuss?

Thanks, Merril

Hello  Merril

Thank you. 

Newman said:

When running at max frequency, could our device be expected to fail w/ "slower than spec'd" inputs.. or has it just not been characterized at these slower rise-times?  ?

As i understand to meet the timing requirements at max speed, the slew rate is required to be in the specified range.

Newman said:

What do you recommend the customer do? 

Is customer doing analysis or seeing some functional or performance issues.

With a slower operating frequence, i suspect the slew rate requirements would change but as mentioned above this has not been characterized.

I would refer to below section for the LVCMOS slew rate

7.7.6 LVCMOS Electrical Characteristics

Regards,

Sreenivasa