Testing a Assembled Board

[sumavl]

Hi All,


I have a fully assembled board; I would measure the Resistance between VCC (1.2V) & GND on the board before powering on.

The Multimeter shows a reading of 20 ohms.

I have observed usually the core voltage to ground will be in the range of 20-100 Ohms why is it so?

From the above readings, can I infer that the processor would consume a current(minimum) of
60mA (i.e. I=V/R; 1.2V/20) after power-on?

2. If the above is not true, then what conclusions can be drawn from the above reading?

 

[xunzhaoziwo]

you know, I came across a board using ADI TS201 DSPs, the spec says the impedance between GND and VCC should be 50ohm or something like that, but the actual value I measure on the board between GND and VCC is just 8ohm. That time, I thought it must be short!
But after checked all the possible short place, I tried to power on the board, no smoke at all, and worked well. ^_^
Later, I know the impedance we measure between the GND and VCC is the equivalent impedance of many power pins and ground, it is a parallel value of all the power pins, and the equalized value should be smaller than the impedance in the spec. In Spec, the impedance should be measured between ONE PIN and GND.
I Suggest you to check every possible short place, if there is no short, then you can power on! Good luck!