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Noise of LM317-N ..... "ultra low noise" ?

cafemax
Prodigy 110 points
Other Parts Discussed in Thread: LM317-N

Hi,
When I using the LDO product filter,

The noise of LM317-N  shows as 35 uVrms only.

..... I have no idea if a 40yo device has 35 uVrms performance,

what does "ultra low noise" really mean?

(ps. TPS78630 has 48uVrms noise and it called ultralow noise.)

  • Guru 74080 points

    Hi Cafemax!

    The datasheet says it has a noise level of 0.003% of Vout (10Hz...10kHz).

    For an output of 10V, this would be 300µV. So ten times the value. The 35µV would be at an output voltage of 1,167V. But the internal voltage reference of 1.25V also limits the output voltage to 1.25V when ADJ is tied to GND directly. Always rely on the datasheet.

    Dennis