MSP430FR4133: TI's version of RESET circuit

Can you please point out the App Notes with this RST circuit? Noise immunity is probably the goal but I am hesitant to believe that it will communicate successfully with a MSP-FET using R22/C51. I always recommend Figure 2-3 from the Hardware Tools User's Guide (SLAU278).

Regards,
Ryan

Ryan Brown1 said:

Can you please point out the App Notes with this RST circuit?

Here is one:

http://www.ti.com/general/docs/lit/getliterature.tsp?baseLiteratureNumber=tidrax2&fileType=pdf

There are more which slightly vary...

I always recommend Figure 2-3 from the Hardware Tools User's Guide (SLAU278).

This is what I currently use (although w/o R1 as I use the internal one and with 1nF to GND).

That confirms my assumption. However, I wonder why some reference
apps use the one Ryan mentioned and others the one I have in my
first post...

Tom Dehler said:

Part Number: MSP430FR4133

I've seen several APP notes which implement a RESET circuit like this one:

What is the exact reason for doing this? Most data sheets talk only about
a pullup and a 1,1 nF (what a funny value) to GND if one is planning to
use SBW.
 
The 1,1 nF is because programmers can't drive higher capacitive loads.
But can they drive resistive loads like the R22 (which is effectively tied to
ground from an AC point of view in the design from above)?

I this case the R22 / C51 combo is probably there to add some additional
noise immunity. But can I be sure a programmer (like the MSP-FET) can
drive this thing through SBW?
 
Or is there a different reason for all this stuff?

Hi Tom,

You are right. 

Most reset circuit only about a pullup resistor and a 1.1 nF  capacitor to GND if one is planning to use SBW.  
The 1.1 nF is because programmers can't drive higher capacitive loads.

Reset pin is sensitive especially in ESD test. And add uF level capacitor on reset pin improves system ESD performance, but it affects SBW communication. To overcome this, the RESET circuit which you saw in the app note is used.

Regards,

Ling