LM2940 DATASHEET PDF

The LM/LMC positive voltage regulator features the ability to source 1A of output current with a dropout volt- age of typically V and a maximum of. The LM LMC positive voltage regulator features the ability to source 1A of output current with a dropout voltage of typically 0 5V and a maximum of 1V. The LM positive-voltage regulator features the Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

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Less crucial is a picture of the output voltage waveform especially as we don’t know what bad probing techniques you may have used. What is the input voltage? I believe that I have conformed to the guidelines in the datasheet. The capacitor you linked to is 22pf, which is only one millionth of the specified value. What about with satasheet simple resistor load at the same current, does it have the same problem?

Email Required, but never shown. If the schematics is right, your input voltage is too low, the LDR needs some headroom to regulate how much depends on your actual load.

National Semiconductor

I’m encountering some instabilities in my regulated voltage supply. Thanks for your time.

In second case the OKI is highly suggested. I hope you know that the 2 are not properly the same parts, both are 5V regulators but the OKI is switching power supply, while the LM is linear one, the main difference for your use is heat dissipated.

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I have used the LM in a number of designs with no problem using tantalum input and output caps. Hi Russel, eatasheet for the feedback.

LM Datasheet(PDF) – National Semiconductor (TI)

KevinWhite, the 5V net label represents the lowest measured output from the rectifier circuit. My note started from the fact that both regulator are rated at datasbeet input and capable of 1A, and you didn’t initially specify yours needs. As a general rule, the higher the voltage rating the larger the size so a 0. Alas the data on minimum ESR is rather sketchy nothing for “C” case for exampleso you have to guesstimate from just datashest two graphs or get an ESR meter and measure it, or even just with your scope and a function gen that can hit those MHz frequencies where you see oscillation.

Please see updated question with attached schematic. With such low power involved you can go with the linear regulator, you shouldn’t have any problem. Schematic of the regulation circuit. If you look at page 18 in its datasheet the ESR for the uF, 6.

They need km2940 be rated dagasheet my voltages also. You quote the ESR at kHz. Whether the or Hz ESR is relevant is tbd BUT as you have a 2 x mains input ripple that the regulator is dealing with this may be the instability trigger.

Tom Wilson 68 7. Could datashet contribute to the oscillation? Have you taken their compulsory advice re the output capacitor? Russell McMahon k 9 Do you also have the input capacitor 0. Locate as close as possible to the regulator.

Sign up or log in Sign up using Google. Layout and circuit are crucial. The suggested solution in that appnote, figure 7 vs. As, if anything, your ESR may be too high it seems I’d try another cap in parallel.

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If not then what am I looking for exactly. And also separately a resistor in series for belts and braces coverage: Sign up using Email and Password. I have used a ground-plane in my PCB design. Or offer an alternative regulator that is more linear at high frequency As suggested in this answer? You have 5V on the schematic which can’t work.

Your oscillations are at 18 Mhz where the ESR is hopefully very low. The vishay datasheet shows ratasheet of ESR with frequency. CuF is an SMD tant: NB – in the pdf you cite they say: Perhaps I have misunderstood this specification?

Any advice or pointers will be much appreciated! Whether this is really what they intend is unknown. This capacitor must be rated over the same operating temperature range as the regulator and 2 the ESR is critical – see ddatasheet.

I live in Lincoln.

Post as a guest Name. Tying down what manufacturers really mean can be a challenge. I was reading it on my break and was in a hurry. This capacitor must be rated over the same operating temperature range as the regulator and. By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

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