The LM LM series are monolithic frequency to voltage converters with a high gain op amp comparator de- signed to operate a relay lamp or other load. uses a charge pump technique and offers frequency doubling for low ripple, full input protection in two versions (LM,. LM) and its. The LM, LM series are monolithic frequency to voltage converters with a high gain op Details, datasheet, quote on part number: LM

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That chip is made to detect RPM, most engines Idle rpm-ish, so you’re going to need a bunch of pulses or it’s going to measure 0.

Yeah – I figured that i needed a decent ‘frequency’ It is drawn to be a comparator rather than a buffer. How are you pulsing the 14V? Sign up using Facebook. By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policydatasheet our Terms of Service.

National Semiconductor

I feel well past my depth trying to sort this out I’m stuck with a pin LM – i’ve got an 8-pin on order now, but damn it, I want to get this to work. You have fixed Pin 11 at about 0. But how does this charge pump do this?


This is confusing too. Andy aka k 10 I want to learn working principle and internal circuit of the IC, and function of externally connected components especially C What is the function of the second opamp? The load is needed datasheeh convert the stored charge into a voltage that can be sensed, and pragmatically to provide a place for the stored charge to leak off into as frequency falls.

Its om2917 is very old and it doesn’t explain function of the IC well. Then put a 10K resistor to the cathode of D3 and the other end of it to ground.

Problem with LM Tach Circuit – 14 Pin version

Home Questions Tags Users Unanswered. I created a custom library for this IC and set up my own circuit as seen pm2917 the schematics above. And heres my breadboard layout: Page 1 of the data sheet says it all. I guessed the roles of the capacitors completely wrong initially. Its driving me nuts I’m not game to l2917 it to my ‘duino nor can I be buggered going out to the bike yet Im guessing now totally that my ‘test powersupply’ is putting 70ma across the base of thewhich is saturating it.


C41 is a filter capacitor to reduce the ripple from the charge pump. Sign up using Email and Password. I’ve played around with a few variations.

Datasheeet a hand-waving explanation from a digital and software guy who has bumped in to sharp edges in the analog side The second op-amp is buffering the signal stored on C41 and driving the output transistor, it has feedback from the output to its -ve input which is a common configuration for a unit-gain buffer. 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.

Read towards the bottom of datasyeet 8 on the data sheet. An example circuit from the datasheet. Sign up or log in Sign up using Google.

I’m trying to make a frequency-to-voltage converter by using LM The first op-amp datasbeet a camparator as your question states. I need a circuit which generates 1mV voltage per 1Hz frequency.