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REF5025: REFERENCE OF ESR RESISTOR
Part Number: REF5025
The datasheet says the ESR of CL must be less than or equal to 1.5Ω to ensure output stability. My questions are:
1. Why ESR with 1.5Ω or less is required to ensure output stability?
2. What if the ESR is higher than 1.5Ω？
3. At which frequency range should the ESR be 1.5Ω or less?
From the block diagram, the Vout is from an amplifier, usually the phase margin of open loop gain is big at low frequency. The ESR of capacitor at low frequency such as 2.8Ω @100Hz is also higher than 230mΩ@ 1KHz. Does it mean that the ESR should be less than 1.5Ω from 100Hz to 10GHz or just at 1kHz？
Thanks and Best Regards!
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In reply to Ethan T:
I think it maybe misunderstood that the picture by hao wang, it can be seen in more detail from the attached datasheet,
from the datasheet, this curve is show the ESR, and the ESR is greater than 1.5 ohm at low frequencies.
Does this have any effect on this application?
Or we only need to pay attention to the value of ESR when Z=ESR?
In reply to yunlin an:
Got it, thak you very much!
the datasheet says that the ESR must less or equal than 1.5 ohm, and the recommend value is 1-1.5 ohm to minimize the noise
so the question is
Does it means the noise about ESR between 1-1.5 ohm is better than the ESR of 10 mohm ? and do you have any output noise figure of different ESR capacitor?
This a lower than recommended ESR value does not necessarily mean more noise. The device has shown optimized noise performance between the recommended ESR values which why it is stated in the datasheet.
I have attached an excel sheet with some typical bench data between ESR values. It does not measure noise, but shows the range of stability between ESR values.
Hope this helps,
REF5025 Cout ESR Test.xlsx
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