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PIC32MX340F256H Crystal problem

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nagarajkumark

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Hi,
i am using PIC 32MX340F256H. Crystal KDS 8 MHZ, load capacitance 22 PF in OSC1 and OSC2 pins. i have some problem in crystal OSC1 pin . when i the touch crystal OSC1 pin in multimeter probe or CRO probe, it's working good. otherwise its not working. after reseting the board its not working. after touch using multimeter probe or CRO probe its working.
any one please help

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NAGA:sad:
 

Its stray capacitance effect. the value of capacitor may not be enough. if you touch by hand also it will work. see if both are same value. see what is the recommended value. put 22 -33 pf range. solder it properly. It can be due to dry solder also.
 

Thanks for your reply. both load capacitance are same. no dry soldering. still now i soldered 10 numbers of PCB using this controller, but all board are same this problem in starting stage. After any physical interrupt its working perfectly all board. i want to know this which kind of problem. i attached my schematic please give me your suggestion. advance thanks and sorry for broken english. thanks

by
NAGA
 
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i found out that solution. but i want to know this is right or wrong. when i connect 100K resistor and 0.1uF capacitor connected in series across the OSC1 pin . It's working well. [/IMG]
 

it may be the case also.. due to non matching of RC value.. what does the specification document says... but there will be some difference in theoritical and practical implementation
 

I would have considered extra capacitance where you touched the oscilloscope probe rather than that unusual network. Some oscillators put a resistor on the OSC-out pin but I have never seen a circuit like that.

Keith
 

finally 1 mega ohm resistor connected across the OSC1 pin and OSC2 pin. it's working. thanks for your replies.

NAGA
 

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