shorting of digital high and ground


by satya77
Tags: digital, ground, shorting
satya77
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#1
Feb9-12, 09:21 PM
P: 39
Hi,

I generally work on embedded boards so i always had this doubt generally in any embedded board with micro controller the pins on the micro controller are located very very close, so if i am trying to see the voltage or some waveform on any of the pins using oscilloscope or multimeter and if it gets shorted with the adjacent pin or to the ground then does it damage the micro controller. In general what are the pins that should never get shorted. Any suggestions on this will help me to face the hardware more confidently.

Thanks and regards,
Satya
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yungman
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#2
Feb9-12, 09:32 PM
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The only way to have more confident is getting a good low power microscope or a good magnifying glass and very good lighting. Look at it, use a ohmmeter to measure between pins. And then it help you get extra parts to replace and a good solder station to remove and replace the chip!!!!

Seriously, you can only do so much and say a prayer!!! Do the best you can and cross your finger. You got to move on at some point of time. Double check, look carefully. That's all you can do. It die, you cry!!!!

I am not being bad, it's just life. If you never smoked up the room, you're not an engineer!!! I just did!!! I just smelled the dragged smell of a pan fried opamp last week!!! I was so careful to check all the pins and hooked up Vee to +V and Vcc to ground!!!!
cepheid
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#3
Feb9-12, 11:21 PM
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Quote Quote by satya77 View Post
In general what are the pins that should never get shorted. Any suggestions on this will help me to face the hardware more confidently.
Also, I don't know that we can really give you a general statement about what pins should never be shorted. It depends upon the chip and circuit in question. Generally speaking, shorting power to ground is usually bad, but it's tough to say in general how much damage might ensue. Some chips have overcurrent protection. Yungman's advice to just be more careful, although it may sound trite, is probably the best thing we can say. Also, having the right tools can help a lot. If you can afford it, maybe you can look into getting some ultra thin probes that are designed for surface mount ICs etc.

A trick I once used was to temporarily solder a wire to each pin that you are trying to probe. Then you can clip the scope/multimeter probes to the free ends of those wires, which can be much farther apart from each other. However, this soldering itself may be tricky on surface-mount ICs with very closely-spaced pins. I can't remember now, but I think I may have managed it on one surface mount IC and a couple of through-hole DIP ones.


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