PCBA power supply short circuit analysis method
2023-12-28
When dealing with hardware, it is inevitable to encounter some pins of the PCBA or a short circuit in the network. Among them, the most difficult thing is the problem of short circuit of power supply, especially the board is more complex, there are many circuit modules, including BGA and other chips are not easy to measure, such as 3.3V short circuit.
PCBA power supply short circuit, maybe everyone will generally check level by level. In the case that the visual inspection does not find any problems such as tin, first check whether the corresponding power chip is broken (disconnect the post-circuit circuit to see that it is a short circuit), and then see which circuit modules of the short-circuited network use this power supply, at this time, the magnetic beads or 0Ω connected in series on the power supply play a role. Slowly eliminate and narrow down the range until you finally find the short-circuited device.
The above method is naturally correct, but there is a problem that it is inefficient, and it depends on luck, and you can find it if you are lucky.
Here's a tried-and-true analysis: the heat analysis
Introduction to the analysis method:
The fever analysis method is the author's own name. Generally, if the board is not short-circuited to tin, such as the chip is broken, or the capacitor is broken, the GND resistance is generally not 0Ω, more or less there will be a few ohms or a few tenths of an ohm, and you can quickly locate it by using this feature.
Using a DC regulated power supply, adjust the power supply voltage to the voltage of the short-circuit power supply (3.3V short-circuit will be adjusted to 3.3V), set the current limiting mode, and the current limiting can be set to 500mA first, depending on the actual situation.
Disconnect the power supply of the PCBA board, connect the set power supply, and see where the circuit board is hot, and where it is hot, it is generally where it is short-circuited.
To see where the heat is hot can be seen with a thermal imaging camera. If you don't have a thermal imaging camera, you can touch it with your hands and feel it (be careful not to burn).
Notes:
The current limiting setting of the DC source needs to be determined according to the actual situation, the current limiting setting is too small, the heating is not obvious, and the problem cannot be found, and the setting is too large and may burn the copper wire on the PCB.
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