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The spectrum of the noise is supplied and here is a copy: -

enter image description here

The noise at 5.5 kHz is a level of 250 uV RMS.

A typical noise/ripple level from a circuit like the one you have is probably around 100 times higher and you appear to be worried by this level.

Yes , we are making it under 1uV (0-20Khz)

The only chance of this happening is if you use a LDO linear voltage regulator fed from the flyback output. Even then I think you are going to struggle.

Take for example the TLV705 that is described by TI as being low noise. It has a quoted noise level of 27 uV RMS across 10 Hz to 100 kHz and it is: -

A LINEAR VOLTAGE REGULATOR AND NOT A SWITCHING REGULATOR

Take the LP5907 as another example. It is described as a: -

250mA Ultra-Low-Noise Low-IQ LDO

Notice my emphasis on the low noise bit. It has a noise output level over a 10 Hz to 100 kHz bandwidth of 6.5 uV RMS.

What you are hoping to achieve is not going to happen with a simple Flyback converter.


MORE CONTEXT

The thermal noise across a 100 kHz bandwidth from a 560 ohm resistor at an elevated temperature of 50 degC (not unheard of in a flyback converter) is 1 uV RMS. At a 20 kHz BW it is about 0.45 uV.

How many resistors have you got in your circuit that are in the signal chain that will add noise to the output? I count 4 and these alone will tip the balance. Be realistic.

The spectrum of the noise is supplied and here is a copy: -

enter image description here

The noise at 5.5 kHz is a level of 250 uV RMS.

A typical noise/ripple level from a circuit like the one you have is probably around 100 times higher and you appear to be worried by this level.

Yes , we are making it under 1uV (0-20Khz)

The only chance of this happening is if you use a LDO linear voltage regulator fed from the flyback output. Even then I think you are going to struggle.

Take for example the TLV705 that is described by TI as being low noise. It has a quoted noise level of 27 uV RMS across 10 Hz to 100 kHz and it is: -

A LINEAR VOLTAGE REGULATOR AND NOT A SWITCHING REGULATOR

Take the LP5907 as another example. It is described as a: -

250mA Ultra-Low-Noise Low-IQ LDO

Notice my emphasis on the low noise bit. It has a noise output level over a 10 Hz to 100 kHz bandwidth of 6.5 uV RMS.

What you are hoping to achieve is not going to happen with a simple Flyback converter.

The spectrum of the noise is supplied and here is a copy: -

enter image description here

The noise at 5.5 kHz is a level of 250 uV RMS.

A typical noise/ripple level from a circuit like the one you have is probably around 100 times higher and you appear to be worried by this level.

Yes , we are making it under 1uV (0-20Khz)

The only chance of this happening is if you use a LDO linear voltage regulator fed from the flyback output. Even then I think you are going to struggle.

Take for example the TLV705 that is described by TI as being low noise. It has a quoted noise level of 27 uV RMS across 10 Hz to 100 kHz and it is: -

A LINEAR VOLTAGE REGULATOR AND NOT A SWITCHING REGULATOR

Take the LP5907 as another example. It is described as a: -

250mA Ultra-Low-Noise Low-IQ LDO

Notice my emphasis on the low noise bit. It has a noise output level over a 10 Hz to 100 kHz bandwidth of 6.5 uV RMS.

What you are hoping to achieve is not going to happen with a simple Flyback converter.


MORE CONTEXT

The thermal noise across a 100 kHz bandwidth from a 560 ohm resistor at an elevated temperature of 50 degC (not unheard of in a flyback converter) is 1 uV RMS. At a 20 kHz BW it is about 0.45 uV.

How many resistors have you got in your circuit that are in the signal chain that will add noise to the output? I count 4 and these alone will tip the balance. Be realistic.

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source | link

The spectrum of the noise is supplied and here is a copy: -

enter image description here

The noise at 5.5 kHz is a level of 250 uV RMS.

A typical noise/ripple level from a circuit like the one you have is probably around 100 times higher and you appear to be worried by this level.

Yes , we are making it under 1uV (0-20Khz)

The only chance of this happening is if you use a LDO linear voltage regulator fed from the flyback output. Even then I think you are going to struggle.

Take for example the TLV705 that is described by TI as being low noise. It has a quoted noise level of 27 uV RMS across 10 Hz to 100 kHz and it is: -

A LINEAR VOLTAGE REGULATOR AND NOT A SWITCHING REGULATOR

Take the LP5907 as another example. It is described as a: -

250mA Ultra-Low-Noise Low-IQ LDO

Notice my emphasis on the low noise bit. It has a noise output level over a 10 Hz to 100 kHz bandwidth of 6.5 uV RMS.

What you are hoping to achieve is not going to happen with a simple Flyback converter.

The spectrum of the noise is supplied and here is a copy: -

enter image description here

The noise at 5.5 kHz is a level of 250 uV RMS.

A typical noise/ripple level from a circuit like the one you have is probably around 100 times higher and you appear to be worried by this level.

Yes , we are making it under 1uV (0-20Khz)

The only chance of this happening is if you use a LDO linear voltage regulator fed from the flyback output. Even then I think you are going to struggle.

The spectrum of the noise is supplied and here is a copy: -

enter image description here

The noise at 5.5 kHz is a level of 250 uV RMS.

A typical noise/ripple level from a circuit like the one you have is probably around 100 times higher and you appear to be worried by this level.

Yes , we are making it under 1uV (0-20Khz)

The only chance of this happening is if you use a LDO linear voltage regulator fed from the flyback output. Even then I think you are going to struggle.

Take for example the TLV705 that is described by TI as being low noise. It has a quoted noise level of 27 uV RMS across 10 Hz to 100 kHz and it is: -

A LINEAR VOLTAGE REGULATOR AND NOT A SWITCHING REGULATOR

Take the LP5907 as another example. It is described as a: -

250mA Ultra-Low-Noise Low-IQ LDO

Notice my emphasis on the low noise bit. It has a noise output level over a 10 Hz to 100 kHz bandwidth of 6.5 uV RMS.

What you are hoping to achieve is not going to happen with a simple Flyback converter.

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source | link

The spectrum of the noise is supplied and here is a copy: -

enter image description here

The noise at 5.5 kHz is a level of 250 uV RMS.

A typical noise/ripple level from a circuit like the one you have is probably around 100 times higher and you appear to be worried by this level.

Yes , we are making it under 1uV (0-20Khz)

The only chance of this happening is if you use a LDO linear voltage regulator fed from the flyback output. Even then I think you are going to struggle.