PIC 12F509 begins to heat at power up

[mackrackit]

What do you have connected to the PIC?
Do you have TRIS? statements at the beginning of your code to control the pin's direction?

[Acetronics2]

Hi,

I got such a surprise , years ago with a 16C84 ... ( Andeas Voggender R/C Esc , showns in Elektor Magazine - project 960095-11 ).

While receiving too much glitches, the PIC begins to heat ... one and only solution : power OFF !!!

No overloaded output ...

Back to the " constructive " side ... you must take great care to the config sequence of your PIC, and especially to the reset circuitry.

When the device starts normal operation (exits the
reset condition), device operating parameters (voltage,
frequency, temperature, ...) must be met to ensure
operation. If these conditions are not met, the device
must be held in reset until the operating parameters are
met

these lines are "not so innocent" ...

see Datasheet related pages for that ...

Alain

PS : could you join the " faulty " program ???

[Pedro Pinto]

Hello Acetronics

I think the problem is the Pic itself. I have until 2 years ago 1000 boards that
have not this problems, for 4 Months have make more 200 units and receive 6
boards back from customers that have this problems.

The init part of the code is very simple

sorry, this a original init code, the previous was experiments

DEFINE OSCCAL_2K 1
'
sepic_ok var GPIO.3        
call_shutdown var GPIO.4
sepic_on_off var GPIO.5
pulsador var GPIO.2
am_on_off var GPIO.1
'sense var GPIO.0
'
TRISIO = %11001111
'
low sepic_on_off        
low call_shutdown       
'						
ciclo var word
conta var byte 
conta2 var byte
flag_pulsador var byte 
'			
DEFINE DEBUG_REG GPIO   
DEFINE DEBUG_BIT 4
DEFINE DEBUG_BAUD 2400
DEFINE DEBUG_MODE 1          '1= direct to pic
DEFINE DEBUG_PACING 1000			
'

	DEBUG "V1.1 08/07",10,13
'
pause 500    'estabilise

ini:low call_shutdown   
ciclo = 1:pause 10
if pulsador = 1 then ini   
 for ciclo = 1 to 100      ' "debounce"
  if pulsador = 1 then ini
   pause 1
 next ciclo 

'Learn if it a switch or a press button
inicia:  
High sepic_on_off        'set Buck/Boost on
 pause 1000              
 for ciclo =  1 to 50    'test if the Buck/Boost works
   if sepic_ok = 0 then 
   for conta = 1 to 100
    pause 10
    if sepic_ok = 1 then learn
   next conta
   low sepic_on_off       'sepic not OK, shut down
    pause 3000
     goto ini
   endif

The rest of the code is a loop to look for shut down by the user or if the sepic not working

Best regards
Pedro

[mackrackit]

Bad set of boards. Seems pretty clear now.

[Pedro Pinto]

Hello mackrackit
What do you mean?
Bad set of boards. Seems pretty clear now.


Regards
Pedro

[mackrackit]

Same old code, same chip, new batch of boards.
Check for a bad trace.

[ErnieM]

Same old code, same chip, new batch of boards.
Check for a bad trace.

OR... new revision silicon is acting up (doubtful).

Interesting problem, current is going somewhere, but current isn't a directly measurable quantity suck as voltage is. Good news is you only have 6 I/O pins to check.

Depending on how repeatable the problem and how disposable a board is you could try removing one pin at a time to see who the current hog is, then seeing if you can switch on the big current if you put the offending pin back in.

One thing to check is if an INPUT is causing the problem: if an input goes to about half Vdd then it will draw a big current (thru Vdd->Vss, not the pin itself).