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I am somewhat new to electronics and am trying to get the output of an LM350T_NOPB voltage regulator to have less than 50mV line noise at all loads <= 3A. Please refer to the schematic, oscilloscope screen shot, and datasheet link below for the following discussion.

The problem is there existsis a 4.1MHz oscillation on the output of the LM350T ranging in excess of 600mVpp that starts at just a few mA output. I can reduce the amplitude of this oscillation to about 80-210mVpp (depending on load) with a 22uF capacitor from output to ground.

I do not understand the origins of this oscillation. I would also like to reduce it to <=50mVpp or even eliminate it altogether.

On page 6 of the data sheet, under "External Capacitors", they mention "like any feedback circuit, certain values of external capacitance can cause excessive ringing" and that a capacitor placed from output to ground can "swamp" the effect. They recommend a 25uF electrolytic capacitor.

Is this feedback circuit ringing that I am observing?

I am also having trouble determining which specification applies to this oscillation in terms of output voltage tolerance.

I have found a specification on page 3 of the datasheet entitled "RMS Output Noise, % of Vout" which lists a specification of "0.001% of Vout" for "10Hz-10KHz" but am unsure if this applies to this oscillation because the frequency and amplitude this troublesome oscillation are far higher than that listed in the specification.

I would very much appreciate any help in understanding this issue and any suggestions on how I may reduce further or eliminate this oscillation.

Thanks.

LM350T Info: https://www.ti.com/product/LM350-N LM350T Datasheet: https://www.ti.com/lit/gpn/lm350-n

Schematic:

enter image description here

Screen Shotshot:

enter image description here

I am somewhat new to electronics and am trying to get the output of an LM350T_NOPB voltage regulator to have less than 50mV line noise at all loads <= 3A. Please refer to the schematic, oscilloscope screen shot, and datasheet link below for the following discussion.

The problem is there exists a 4.1MHz oscillation on the output of the LM350T ranging in excess of 600mVpp that starts at just a few mA output. I can reduce the amplitude of this oscillation to about 80-210mVpp (depending on load) with a 22uF capacitor from output to ground.

I do not understand the origins of this oscillation. I would also like to reduce it to <=50mVpp or even eliminate it altogether.

On page 6 of the data sheet, under "External Capacitors", they mention "like any feedback circuit, certain values of external capacitance can cause excessive ringing" and that a capacitor placed from output to ground can "swamp" the effect. They recommend a 25uF electrolytic capacitor.

Is this feedback circuit ringing that I am observing?

I am also having trouble determining which specification applies to this oscillation in terms of output voltage tolerance.

I have found a specification on page 3 of the datasheet entitled "RMS Output Noise, % of Vout" which lists a specification of "0.001% of Vout" for "10Hz-10KHz" but am unsure if this applies to this oscillation because the frequency and amplitude this troublesome oscillation are far higher than that listed in the specification.

I would very much appreciate any help in understanding this issue and any suggestions on how I may reduce further or eliminate this oscillation.

Thanks.

LM350T Info: https://www.ti.com/product/LM350-N LM350T Datasheet: https://www.ti.com/lit/gpn/lm350-n

Schematic:

enter image description here

Screen Shot:

enter image description here

I am somewhat new to electronics and am trying to get the output of an LM350T_NOPB voltage regulator to have less than 50mV line noise at all loads <= 3A. Please refer to the schematic, oscilloscope screen shot, and datasheet link below for the following discussion.

The problem is there is a 4.1MHz oscillation on the output of the LM350T ranging in excess of 600mVpp that starts at just a few mA output. I can reduce the amplitude of this oscillation to about 80-210mVpp (depending on load) with a 22uF capacitor from output to ground.

I do not understand the origins of this oscillation. I would also like to reduce it to <=50mVpp or even eliminate it altogether.

On page 6 of the data sheet, under "External Capacitors", they mention "like any feedback circuit, certain values of external capacitance can cause excessive ringing" and that a capacitor placed from output to ground can "swamp" the effect. They recommend a 25uF electrolytic capacitor.

Is this feedback circuit ringing that I am observing?

I am also having trouble determining which specification applies to this oscillation in terms of output voltage tolerance.

I have found a specification on page 3 of the datasheet entitled "RMS Output Noise, % of Vout" which lists a specification of "0.001% of Vout" for "10Hz-10KHz" but am unsure if this applies to this oscillation because the frequency and amplitude this troublesome oscillation are far higher than that listed in the specification.

I would very much appreciate any help in understanding this issue and any suggestions on how I may reduce further or eliminate this oscillation.

Schematic:

enter image description here

Screen shot:

enter image description here

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Pat
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Problem with output oscillation of voltage regulator

I am somewhat new to electronics and am trying to get the output of an LM350T_NOPB voltage regulator to have less than 50mV line noise at all loads <= 3A. Please refer to the schematic, oscilloscope screen shot, and datasheet link below for the following discussion.

The problem is there exists a 4.1MHz oscillation on the output of the LM350T ranging in excess of 600mVpp that starts at just a few mA output. I can reduce the amplitude of this oscillation to about 80-210mVpp (depending on load) with a 22uF capacitor from output to ground.

I do not understand the origins of this oscillation. I would also like to reduce it to <=50mVpp or even eliminate it altogether.

On page 6 of the data sheet, under "External Capacitors", they mention "like any feedback circuit, certain values of external capacitance can cause excessive ringing" and that a capacitor placed from output to ground can "swamp" the effect. They recommend a 25uF electrolytic capacitor.

Is this feedback circuit ringing that I am observing?

I am also having trouble determining which specification applies to this oscillation in terms of output voltage tolerance.

I have found a specification on page 3 of the datasheet entitled "RMS Output Noise, % of Vout" which lists a specification of "0.001% of Vout" for "10Hz-10KHz" but am unsure if this applies to this oscillation because the frequency and amplitude this troublesome oscillation are far higher than that listed in the specification.

I would very much appreciate any help in understanding this issue and any suggestions on how I may reduce further or eliminate this oscillation.

Thanks.

LM350T Info: https://www.ti.com/product/LM350-N LM350T Datasheet: https://www.ti.com/lit/gpn/lm350-n

Schematic:

enter image description here

Screen Shot:

enter image description here