Jag provade just att sätta dit en konding på 4.7 microF mellan +5V och Gnd i en koppling med en Pic12F675 med spänningen på.
Picen hängde sig och blir långsamt varmare, efter 10 sek var den skållhet.
Jag testade igen med samma resultat.
Picen verkar inte ha tagit skada av behandlingen iaf.
Det har hänt att Picar har spontan-brunnit(stora bruna gropar i mina labbplattor) och det här visar ju att picar kan befinna sig i ett tillstånd där dom långsamt brinner upp även fast Watchdog är aktiverad.
Nån som har haft liknande erfarenheter?
Nån som kan förklara fenomenet?
Nån som vill testa det jag gjorde(på egen risk)?
Skållhet Pic
Jag har också eldat några 12f675. Det berodde dock på avsaknad av tillräcklig glättningskonding i nätdelen. Varje gång jag slog på lysröret över arbetsbänken började det lukta bränt, blir ju lite spikar vid tändning....
Tog ett tag innan jag kom fram till vad det berodde på. Mica PIC:ar satt dock inte i en labbplatta utan var ytmonterade saker fastlödda på en kretskort - lödtennet smälte och det gick att lyfta bort kretsen!
Tog ett tag innan jag kom fram till vad det berodde på. Mica PIC:ar satt dock inte i en labbplatta utan var ytmonterade saker fastlödda på en kretskort - lödtennet smälte och det gick att lyfta bort kretsen!
Ni kanske är intesserade av vad microchip har att säga.
Mitt andra inlägg kan verka lite "goddag yxskaft" men faktum är att det jag svarade på togs bort och byttes ut mot ett senare svar.
Chribbe:
If I connect a capacitor at 4.7microF in paralell of the power in a circuit with a Pic12F675 when the power is on then the Pic hangs and starting to get warmer.
After 10seconds the Pic is really hot.
If I turn the power off and on then it's working ok.
This thing has happened with other Pics just for no reason.
What is this strange state that causes the Pics to burn?
Support:
Take a scope and scope your Vdd line if it bounces around it is the voltage regulator circuit. Some voltage regulators are very specific on the amount of capacitance you can put on them. If this is the case you must redesign your regulator circuit.
Chribbe:
No, I can burn the Pic even if I connect a pulldown(10Kohm) on all io pins.
This must be something else.
Support:
Even though you have the 10k resistor are driving any of you I/O pins above VDD or violating any of the maximum rating specifications listed on page page 83 of the data sheet. Here is a link to a recent rev. of the PIC12F629/675 data sheet.
PIC12F675
http://ww1.microchip.com/downloads/en/D ... 41190c.pdf
Chribbe:
What I mean is that I can burn up the pic with only pulldowns on the io pins, nothing else is connected, just +5V to VDD and 0V to VSS
Support:
Take a scope and scope your Vdd line if it bounces around it is the voltage regulator circuit. Some voltage regulators are very specific on the amount of capacitance you can put on them. If this is the case you must redesign your regulator circuit
Chribbe:
I have no scope to test it with but I can burn the Pic with just a battery at 4.8V as powersource.
The thing is that I don't have a problem with this, It's Microchips problem.
Apparently they have made a serious misstake with the architecture 'cos a microcontroller should never get into a state where it shortcircuit itself and literally burns.
If Microchip isn't aware of this I think the testlab should have a seriuos look att it.
When I tried it with a battery istead of a Powersupply I hade to connect the capacitor for about 50 times before the Pic hang(the capacitor must of course be discharged before connect).
As I said before, Pics can get into a state like this spontaneously.
Please let me know that you are going to do about this!
Support:
With all due respect we sell millions of the PIC12F675 it is a very solid design and we are aware of no problems especially with which you describe.
Please send us you code and your schematic for review.
Support:
I have waited for days for the information I requested; I must now resolve your ticket.
Chribbe:
Now I have tried this with a new Pic12F675 without any stuff connected, just +5V to VDD and 0V to VSS.
The configbits: __CONFIG _CP_OFF & _CPD_OFF & _BODEN_ON & _MCLRE_OFF & _WDT_ON & _PWRTE_ON & _INTRC_OSC_NOCLKOUT
The program is just an eternal loop.
When I connect a capacitor at 4.7microF to the powersupply when the power is on then the Pic gets very hot.
I left it in this state for several minutes and the Pic seem to handle this hi temperature.
I really want to know what is going on in the Pic at this hi temperature state.
(This is the quickest support I have ever seen, Good work so far)
Support:
Explained he must change T3CCP < 2:1> value to choose a timer other than just TMR2 (and other than just TMR4) in order to have different frequencies. The slowest possible frequency in PWM mode is 1:16 prescaler, and /256 for PR2=255. He is running at 20 MHz, so this gives:
20 MHz / 4 = 5 MHz instruction rate
5 MHz / 16 / 255 = 1.22kHz.
Support:
Are (touching) connecting the cap. while the part is on.
When I connect a capacitor at 4.7microF to the power supply when the power is on then the Pic gets very hot.
Have you considered the large transient current when putting it in contact with the powered chip , while the cap. is instantaneously charging.
It seems as though the part is latching up since it is getting hot. Latch up is were the supply is shorting to ground. The regulator can limit the chip to the point were it deos not get damaged.
Mitt andra inlägg kan verka lite "goddag yxskaft" men faktum är att det jag svarade på togs bort och byttes ut mot ett senare svar.
Chribbe:
If I connect a capacitor at 4.7microF in paralell of the power in a circuit with a Pic12F675 when the power is on then the Pic hangs and starting to get warmer.
After 10seconds the Pic is really hot.
If I turn the power off and on then it's working ok.
This thing has happened with other Pics just for no reason.
What is this strange state that causes the Pics to burn?
Support:
Take a scope and scope your Vdd line if it bounces around it is the voltage regulator circuit. Some voltage regulators are very specific on the amount of capacitance you can put on them. If this is the case you must redesign your regulator circuit.
Chribbe:
No, I can burn the Pic even if I connect a pulldown(10Kohm) on all io pins.
This must be something else.
Support:
Even though you have the 10k resistor are driving any of you I/O pins above VDD or violating any of the maximum rating specifications listed on page page 83 of the data sheet. Here is a link to a recent rev. of the PIC12F629/675 data sheet.
PIC12F675
http://ww1.microchip.com/downloads/en/D ... 41190c.pdf
Chribbe:
What I mean is that I can burn up the pic with only pulldowns on the io pins, nothing else is connected, just +5V to VDD and 0V to VSS
Support:
Take a scope and scope your Vdd line if it bounces around it is the voltage regulator circuit. Some voltage regulators are very specific on the amount of capacitance you can put on them. If this is the case you must redesign your regulator circuit
Chribbe:
I have no scope to test it with but I can burn the Pic with just a battery at 4.8V as powersource.
The thing is that I don't have a problem with this, It's Microchips problem.
Apparently they have made a serious misstake with the architecture 'cos a microcontroller should never get into a state where it shortcircuit itself and literally burns.
If Microchip isn't aware of this I think the testlab should have a seriuos look att it.
When I tried it with a battery istead of a Powersupply I hade to connect the capacitor for about 50 times before the Pic hang(the capacitor must of course be discharged before connect).
As I said before, Pics can get into a state like this spontaneously.
Please let me know that you are going to do about this!
Support:
With all due respect we sell millions of the PIC12F675 it is a very solid design and we are aware of no problems especially with which you describe.
Please send us you code and your schematic for review.
Support:
I have waited for days for the information I requested; I must now resolve your ticket.
Chribbe:
Now I have tried this with a new Pic12F675 without any stuff connected, just +5V to VDD and 0V to VSS.
The configbits: __CONFIG _CP_OFF & _CPD_OFF & _BODEN_ON & _MCLRE_OFF & _WDT_ON & _PWRTE_ON & _INTRC_OSC_NOCLKOUT
The program is just an eternal loop.
When I connect a capacitor at 4.7microF to the powersupply when the power is on then the Pic gets very hot.
I left it in this state for several minutes and the Pic seem to handle this hi temperature.
I really want to know what is going on in the Pic at this hi temperature state.
(This is the quickest support I have ever seen, Good work so far)
Support:
Explained he must change T3CCP < 2:1> value to choose a timer other than just TMR2 (and other than just TMR4) in order to have different frequencies. The slowest possible frequency in PWM mode is 1:16 prescaler, and /256 for PR2=255. He is running at 20 MHz, so this gives:
20 MHz / 4 = 5 MHz instruction rate
5 MHz / 16 / 255 = 1.22kHz.
Support:
Are (touching) connecting the cap. while the part is on.
When I connect a capacitor at 4.7microF to the power supply when the power is on then the Pic gets very hot.
Have you considered the large transient current when putting it in contact with the powered chip , while the cap. is instantaneously charging.
It seems as though the part is latching up since it is getting hot. Latch up is were the supply is shorting to ground. The regulator can limit the chip to the point were it deos not get damaged.
