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Kai Klaas
12/03/12 07:05
Read: 948 times
Germany


 
#188953 - Some datasheets show numbers...
Responding to: Richard Erlacher's previous message
Daniel said:
Hi Kai, Richard, clearly is NOT a problem with Vcc rise/fall time. Seems connected with the moment the clock stops.

Yes, dear Daniel. But in the past we have discussed this topic a lot and in those cases improper power-on-reset and power-on slope rates were an issue.

Richard said:
If you can provide a link to a datasheet or other document that specifies details of Vcc rise and fall, I would be very grateful.

You can find these data in more and more modern microcontrollers, because the manufacturers have realized in the mean time, that there's a problem with isp capable flash micros and improper power-on rise times in combination with the internal POR and BOR circuitry.

Some data can be found here, e.g.:

http://ww1.microchip.com/downloads...39755a.pdf
http://www.atmel.com/Images/doc8161.pdf
http://www.nxp.com/documents...PC92X1.pdf

Now you can say, it's only the POR and BOR which need the controlled Vcc rise times. But I think, everything else inside the micro, for instance the auxiliary oscillators and charge pumps for the flash programming high voltage, etc., is adjusted to that specified power-on slope rate window as well.

I have made good experiences by controlling the power-on slope rate. I never had a flash crash so far.

It's not too tricky to control the slope rate of Vcc. If you power the micro by a switcher, you can use the soft-start control. If you power it by a LM317, you can choose a suited cap at the adjust pin. In battery powered applications a high side switch with a PMOS and a suited gate cap can be helpful. Even a simple RC-element can do the job.

Kai Klaas

List of 33 messages in thread
TopicAuthorDate
C8051F231 experiences      Daniel Contarino      11/30/12 14:43      
   another solution      Erik Malund      11/30/12 15:11      
   The probabilities are low...      Daniel Contarino      11/30/12 18:34      
      think about what happens when you add a finger      Richard Erlacher      11/30/12 22:55      
         The point is ...      Daniel Contarino      12/01/12 03:08      
            Yes ... the underlying issue is the flash ...       Richard Erlacher      12/01/12 11:28      
               Out of my office, but...      Daniel Contarino      12/01/12 14:05      
                  Don't think in Vcc, ESD or hum...      Daniel Contarino      12/02/12 09:24      
   Apparently several C8051F2xx parts have the same pinout      Richard Erlacher      12/01/12 14:25      
   Characteristic for in system programmable flash micros...      Kai Klaas      12/01/12 18:25      
      All too true ... sadly ...       Richard Erlacher      12/01/12 20:13      
         Power-on slope rate...      Kai Klaas      12/02/12 05:31      
            Sorry, my post should be here, no up there...      Daniel Contarino      12/02/12 09:58      
            Have you any basis for that rate?      Richard Erlacher      12/02/12 10:15      
               Vdd ramp time      Maarten Brock      12/03/12 06:15      
               Some datasheets show numbers...      Kai Klaas      12/03/12 07:05      
                  Those aren't the "usual" 805x-core MCU's      Richard Erlacher      12/03/12 17:43      
                     There aren't many "usual" 8051-cores anymore...      Kai Klaas      12/03/12 18:13      
                        How dangerous power ups can be...      Kai Klaas      12/04/12 06:20      
                           I believe it      Richard Erlacher      12/04/12 08:59      
                              (dV/dt) examples      Jim Granville      12/04/12 13:14      
                                 They don't know it either...      Kai Klaas      12/04/12 18:49      
                                    dV/dT etc       Jim Granville      12/04/12 21:39      
                                       reset request...      Kai Klaas      12/05/12 06:21      
                                          That's what disturbs me greatly      Richard Erlacher      12/06/12 00:19      
                                             It IS disturbing!      Kai Klaas      12/06/12 08:02      
                                                Where this began ... at least for me ...       Richard Erlacher      12/06/12 09:43      
                                                   So, you took the hard road...      Kai Klaas      12/06/12 10:41      
                                                      We've all had that experience       Richard Erlacher      12/06/12 16:23      
   probable cause      Brent Wilson      02/04/13 20:32      
      Brent, this is very nice      Erik Malund      02/05/13 06:38      
         forum no longer down      Maarten Brock      02/05/13 07:33      
      Thank you!      Daniel Contarino      02/05/13 15:04      

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