Electronics > Projects, Designs, and Technical Stuff
Voltage regulator, LDO + PSRR (10+ kHz), does they exist?
MasterT:
For a project I'm working on, I need a regulator +7.5V that satisfy two simple requirements LDO & PSRR.
I see, there are lm317 and all 78xx series, that have good PSRR above 10 kHz (-70 dB or so up to 20+ kHz) but not LDO.
On the other side modern mosfet p-channel LDO's that have miserable low PSRR, about -10 dB, some companies even don't publish any data except 120 Hz. And its strange for me, unlike 40 years ago nobody should care much about 120 Hz rejection since almost all power supplies switchable, and PSRR in the sub-MHz range should be primary goal for good properly designed voltage regulator. And I don't envision any obstacle to build fast circuits , since technology step far away from lm317 manufacturing process.
What, inductors makers rule the market?
Boscoe:
http://www.ti.com/lit/ds/symlink/lp38798.pdf
I found this using TI's parametric search in a minute or so, finding parts is dead easy when you master these things. I use a lot of TI parts as their website and search is particularly good.
ogden:
Champion of LDO's (today): LT3042.
RMS Noise: 0.8µVRMS (10Hz to 100kHz)
PSRR: 79dB at 1MHz
ConKbot:
Make sure you check the datasheet curves for PSRR as you approach dropout, and at your intended running voltages. A regulator may specify a 60+ db PSRR, but that may be at Vin-Vout = 1V, not when it's at 0.2V or lower that the dropout voltage is specified at.
MasterT:
--- Quote from: Boscoe on May 19, 2019, 09:54:30 pm ---http://www.ti.com/lit/ds/symlink/lp38798.pdf
I found this using TI's parametric search in a minute or so, finding parts is dead easy when you master these things. I use a lot of TI parts as their website and search is particularly good.
--- End quote ---
Thanks for the tip, TI search engine is much better than at mouser. Though seeding through hobby friendly package groups, I was able to locate non TO-92, and just 1 part in soic-8 adjustable that goes above 5.0V, with good PSRR data. It's LM2931. There are two more parts LP2951 & LP4951 that have unreliable PSRR over mA current range. Will order 2931, to see how it goes.
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