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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Please see updated question with attached schematic. By using our site, datashedt acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. The vishay datasheet shows change of ESR with frequency. I read the data sheet for the LM and understand I need two capacitors one on the input and one on the output.

Russell McMahon k 9 Whether this is really what they intend is unknown. Tom Wilson 68 7.

Tying down what manufacturers really mean can be a challenge. Your oscillations are at 18 Mhz where the ESR is hopefully very low.

National Semiconductor

I have used a ground-plane in my PCB design. By clicking “Post Your Answer”, you acknowledge that you have read our updated terms of serviceprivacy policy and cookie policyand that your continued use of the website is subject to these policies.

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Thanks for your time.

Home Questions Tags Users Unanswered. In second case the OKI is highly suggested.

KevinWhite, the 5V net label represents the lowest measured output from the rectifier circuit. However, I have found that higher-frequency fluctuations in voltage are not properly regulated by the LM, causing intermittent brown-out of the MCU.

It can be 2x to 4x higher at 2 x mains frequency.

Post as a guest Name. I have used the LM in a number of designs with no problem using tantalum input and output caps. Could that contribute to the oscillation? Schematic of the regulation circuit. 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.

Alas the data on minimum ESR is rather sketchy nothing for “C” case for exampleso you have to guesstimate from just these two graphs or get an ESR meter and measure datasjeet, or even just with your scope and a function gen that can hit those MHz frequencies where you see oscillation.

LM what capacitors?

What about with a simple resistor load at the same current, does it have the same problem? 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.

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I was reading it on my break and was in a hurry. And also separately a resistor in series for belts and braces coverage: This capacitor must be rated over the same operating temperature range as the regulator and. My note started from the fact lm29440 both regulator are rated at 24V input and capable of 1A, and you didn’t initially specify yours needs.

Hi Russel, thanks for the feedback. Post Your Answer Discard By clicking “Post Your Answer”, you acknowledge that you have read our updated terms of serviceprivacy policy and cookie policyand that your continued use of the website is subject to these policies. What is the input voltage? The suggested solution in that appnote, figure 7 vs.

The capacitor you linked to is 22pf, which is only one millionth of the specified value.

National Semiconductor – datasheet pdf

Locate as close as possible to the regulator. Is your automotive environment 12V or 24V? Email Required, but never shown.