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Why the stable supply voltage is "shaked" after connected to the testing board ?

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matrixon

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Why the stable supply voltage is "shaked" after connected to the testing board ?

I used a power supply to supply 1.8V as the Vdd of the tested-circuit,
after I connected 1.8V to the Vdd pad of the testing-board,
the originally "clean" 1.8V began to shake.

The phenomenon can be improved by adding 1uF cap between
Vdd and gnd Pad.
But why the originally clean Vdd is shaked after connected to the testing-board?
 

Re: Why the stable supply voltage is "shaked" after connected to the testing board ?

That may be because, your testing circuit is taking lot of current from the power supply. What amount of current is needed for your circuit ? What is the rating of your power supply?
 

Re: Why the stable supply voltage is "shaked" after connected to the testing board ?

It is of loading issue..Provide the information of supply current and operating current ratings.

Is it properly routed board or else just connecting the circuit with wires?
 

Re: Why the stable supply voltage is "shaked" after connected to the testing board ?

MUKESH.K.S said:
That may be because, your testing circuit is taking lot of current from the power supply. What amount of current is needed for your circuit ? What is the rating of your power supply?
Click to expand...

About 60mA is needed for my circuit,and what is the rating of power supply?

Why the large amount of current taking from power supply can make this effect?

- - - Updated - - -

hobbyckts said:
It is of loading issue..Provide the information of supply current and operating current ratings.

Is it properly routed board or else just connecting the circuit with wires?
Click to expand...

The supply current is about 60mA,and what is the operating current rating?
There is no problem(No fatal DRC error) on the board and no other AC signal connected to the circuit(all inputs are connected to gnd).
 

Re: Why the stable supply voltage is "shaked" after connected to the testing board ?

Operating current rating is the maximum current that your power supply can source. If your circuit is taking more current than the specified current rating, it will overload your power supply and may lead to the problems that you are talking about. If your circuit is having some oscillator circuit, the oscillations will add harmonics to the supply also.In such situations you need to add filtering circuits using capacitors, which will improve the situation.
 

Re: Why the stable supply voltage is "shaked" after connected to the testing board ?

Supply current is what your power supply could able to provide & operating current is at the range your circuit will be working.

So from your answer it seems that your operating current is 60mA. But did you find it out (needed to know whether you measured it correctly)

For finding out the supply current provide the part number of the regulator which you are using in your regulator.
 

Re: Why the stable supply voltage is "shaked" after connected to the testing board ?

hobbyckts said:
Supply current is what your power supply could able to provide & operating current is at the range your circuit will be working.

So from your answer it seems that your operating current is 60mA. But did you find it out (needed to know whether you measured it correctly)

For finding out the supply current provide the part number of the regulator which you are using in your regulator.
Click to expand...

matrixon said:
About 60mA is needed for my circuit,and what is the rating of power supply?

Why the large amount of current taking from power supply can make this effect?

- - - Updated - - -



The supply current is about 60mA,and what is the operating current rating?
There is no problem(No fatal DRC error) on the board and no other AC signal connected to the circuit(all inputs are connected to gnd).
Click to expand...

There is no regulator on the board,I connect 1.8V directly to the header. And I will check the rating current of the power supply.Thanks for your advice.
 

Re: Why the stable supply voltage is "shaked" after connected to the testing board ?

MUKESH.K.S said:
If your circuit is having some oscillator circuit, the oscillations will add harmonics to the supply also.In such situations you need to add filtering circuits using capacitors, which will improve the situation.
Click to expand...

The testing board only contains an op amp I want to test and some I/O ports(SMA,header),and all the inputs of this op amp are connected to ground.
 

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