Narrow down by specifying conditions
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This is Sasaki in charge of power supply dock technology.
In this column, I would like to introduce some examples of problems related to power supplies that I encountered multiple times during various customer support sessions.
After receiving an inquiry that the switching operation of the power supply was becoming unstable, I decided to visit the company and consult with them while observing the actual operation and measured waveforms.
What causes unstable operation of switching regulators?
Regarding the switching waveform of this DC/DC converter, I am having trouble with the on-time becoming short in rare cases.
It seems that the switching control is not working properly.
The power supply or GND supplying the DC/DC converter may be unstable.
That can't be true.
In this design, in order to ensure stable circuit operation, we have increased the number of vias and strengthened the power supply and GND.
That's right.
Just to be sure, let's check the actual machine while looking at the circuit diagram and board layout.
Check schematics and boards
Ok, I understand the reason.
It seems that the measures to strengthen the power supply and GND backfired.
e? !
what do you mean?
The cause is that a via is provided between the GND of the decoupling capacitor and the GND of the DC/DC converter.
Because of the large number of vias, the inductance component of the GND line increases, making operation unstable.
What should I do now?
A countermeasure is to place a decoupling capacitor close to the IC without using a GND via.
Also, too many vias can be a problem, so it would be better to adjust the number to an appropriate number.
understood.
This can't be done with a little modification, so I'm going to change it all at once when I revise the board before mass production.
In that case, would you be willing to consult on board design?
Yes, please feel free to contact us.
We will support you so that you can transition to mass production without any problems.
Cause of unstable switching waveform
The inductance component of the GND line became large due to too many vias.
The point of this time
Too many or too few vias are bad. Make sure you put the right number in the right place.
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