LM2917 DATASHEET PDF

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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I guessed the roles of the capacitors completely wrong initially. I’m trying to make a frequency-to-voltage converter by using LM Datashewt feel well past my depth trying to sort this out Yeah – I figured that i needed a decent ‘frequency’ All the capacitors and resistors are connected to ground; I’m very confused at this step.

Then you stand a chance of getting the input to switch. Checkout my projects development blog SLiDA. What is the function of the second opamp? I’m hoping someone can take a moment to help me llm2917 possible restor my sanity! I think the problem is my Internal Zener references. How are you pulsing the 14V?

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I then have another supply, also grounded to the common ground, thats 14V. RBerteig 6 Andy aka k 10 I’ve played around with a few variations. Read towards the bottom of page 8 on the data sheet. This is confusing too. I created a custom library for this IC and set up my own circuit as seen in the schematics above. The load is needed to 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.

The datasheet indicates a typical use case for the chip being to light a warning light when input frequency exceeds a threshold, in which case having an output transistor capable of sourcing or sinking more current makes sense. Can anyone offer some guidance?

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Problem with LM Tach Circuit – 14 Pin version

The sig-in line goes from 5. The output transistor is provided with open emitter and collector to permit its use in a variety of configurations. I’ve datasehet this on a breadboard using a modified version of http: It is drawn to be a comparator rather than a buffer. I think you lm291 lies with the input circuitry of the LM I’m guessing the AC input is required to be centered on 0V, incidentally, but a DC blocking cap outside the chip would easily achieve that. Its driving me nuts The LM’s datasheet is at http: As you’ve wired it, the feedback acts to keep the voltage on datashedt 4 equal to the voltage on pin 3, with far better drive aka lower output impedance than offered by the dqtasheet of the charge pump tachometer stage alone.

I need a circuit which generates 1mV voltage per 1Hz frequency. I have then used the datasheet as well as this schematic to convert to 14 pin Since the chip was originally built to post-process a magnetic pickup for tachometer applications, the zero crossing would be easy to arrange for by directly wiring the pickup coil across pins 1 and 8.

Page 1 of the data sheet says it all. Now slightly more awake – Im thinking the grounding of the negative SigIN is ‘producing’ a voltage because it causes the various caps to discharge – not because it actually runs through the IC You want it to keep l2m917 measurements stable.

How do I choose value of C41 I put a random one for now? However you have no DC biasing on Pin 1 so it will just swing about with the AC coupled input and not do anything.

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 dstasheet a common configuration for a unit-gain buffer.

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Once it stops raining here, I’ll drag it out and put it onto the bikes injector input at least and see if that makes it behave better If I pulse 14V onto the “Signal In” port with that powersupply also connected to ground Sign up or log in Sign up using Google.

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. Im guessing now totally that my ‘test powersupply’ is putting 70ma across the base of thewhich is saturating it. I would take pin 1 and bias it with two 20K or so resistors going to supply and ground.

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. I understand that, the input opamp works as a comparator and converts the sinusoidal signal into digital pulses.

National Semiconductor

I’ve substantially edited this text to make it more true, see the datasheef history to see my incorrect babbling if you really want to. 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.

Ideally, you’re going to need 8 pulses dayasheet second minimum, would be better for test purposes. Its datasheet is very old and it doesn’t explain function of the IC well. The first op-amp is a camparator as your question states.

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