Electronics > Projects, Designs, and Technical Stuff
Voltage regulator, LDO + PSRR (10+ kHz), does they exist?
MasterT:
--- Quote from: NANDBlog on May 20, 2019, 03:29:16 pm ---Place an RC filter in front of the LDO, and magically now you have good PSRR for high frequencies. 1 Ohm 100uF gives you about -20dB @ 10KHz. With minimal loss in voltage.
--- End quote ---
Could be an option, for 20 mA I can push resistor up to 10 Ohm and get -40dB. Still too low, 18-bits ADC 1.33 msps (EVAL-AD7984-Pxxx) is very sensitive.
My first try to get clean -2.5V / +7.5V power using dc-dc isolated +5/ +-12V than downregulate with lm317l /lm337l turns out a disaster on EMI interference side.
Second build using TC7660 charge pump converter get 6-10 times lower EMI, but I get into the limits of lm317l, loaded converter (with 2x schottky multiplier) supply only 8.8V, and regulator switched itself into bypass - mode.
I put -70db as a base line, and was wondering why there are no lm78xx / lm317 generation-2, or G-3 etc. Some TO-92 easy to use upgrades of the common and very popular ICs. Though, at least I found one (lm2931) with the help of this forum.
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