LM2940 DATASHEET PDF

Perhaps I have misunderstood this specification? Please see updated question with attached schematic. The vishay datasheet shows change of ESR with frequency. For reference, this is the LM datasheet. If you look at page 18 in its datasheet the ESR for the uF, 6. Read 1 time previous topic — next topic.

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I was using datashet above to supply 5v to my Atmegap-pu project in my automotive environment for controlling the signal that datqsheet on some lights via Mosfet. Email Required, but never shown. This capacitor must be rated over the same operating temperature range as the regulator and 2 the ESR is critical — see curve. Sign up using Email and Password. What is the input voltage? Tom Wilson 68 7. Could that contribute to the oscillation? Hi Russel, thanks for the feedback. Any advice or pointers will be much appreciated!

Is your automotive environment 12V or 24V? The vishay datasheet shows change of ESR with frequency. I was reading it on my break and was in a hurry.

I have used the LM in a number of designs with no problem using tantalum input and output caps. National Semiconductor Do you also have the input capacitor 0. Your oscillations are at 18 Mhz where the ESR is hopefully very low. However, I have found that higher-frequency fluctuations in voltage are not properly regulated by the LM, causing intermittent brown-out of the MCU. 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.

If not then what am I looking for exactly. I live in Lincoln. Russell McMahon k 9 This capacitor must be rated over the same operating temperature range as the regulator and. Have you taken their compulsory advice re the output capacitor?

If you look at page 18 in its datasheet the ESR for the uF, 6. 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.

Sorry, that was my mistake. Schematic of the regulation circuit. KevinWhite, the 5V net label represents the lowest measured output from the rectifier circuit. Or offer an alternative regulator that is more linear at high frequency As suggested in this answer? The suggested solution in that dataheet, figure 7 vs. Sign up using Facebook. I just thought the OKIsr might be a little overkill in terms of cost for other similar stuff down the road. Does anyone have any ideas how I might stabilize this output?

Post as a guest Name. The datasheet specifies the drop-out dztasheet as 0. For reference, this is the LM datasheet. I read the data sheet for the LM and understand I need two capacitors one on the input and one on the output. By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. 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.

May be increased without bound to maintain regulation during transients. Related Posts.

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I was using datashet above to supply 5v to my Atmegap-pu project in my automotive environment for controlling the signal that datqsheet on some lights via Mosfet. Email Required, but never shown. This capacitor must be rated over the same operating temperature range as the regulator and 2 the ESR is critical — see curve. Sign up using Email and Password. What is the input voltage?

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National Semiconductor

You quote the ESR at kHz. Schematic of the regulation circuit. I believe that I have conformed to the ddatasheet in the datasheet. Tom Wilson 68 7.

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Furthermore, a quiescent current reduction circuit has been included which reduces the ground current when the differential between the input voltage and the output voltage exceeds approximately 3V. The quiescent current with 1A of output current and an inputoutput differential of 5V is therefore only 30 mA. During line transients, such as load dump when the input voltage can momentarily exceed the specified maximum operating voltage, the regulator will automatically shut down to protect both the internal circuits and the load. Familiar regulator features such as short circuit and thermal overload protection are also provided. Features n n n n n n n Dropout voltage typically 0. May be increased without bound to maintain regulation during transients.

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