LM2917 PDF

versions (LM, LM) and its output swings. Solenoids, Meters, or LEDs to ground for a zero frequency input. • Frequency Doubling For Low Ripple. Texas Instruments LMN Series Voltage to Frequency & Frequency to Voltage are available at Mouser Electronics. Mouser offers inventory, pricing. LM LM – Frequency to Voltage Converter, Package: Soic Narrow, Pin Nb= The LM, LM series are monolithic frequency to voltage.

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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. Llm2917 quick look at the datasheet suggests the diode on the input isn’t necessary, it seems desined to have the tach ac input, no experience with the ic tho.

I want to learn working principle and internal circuit of the IC, and function of externally connected components especially C I guessed the roles of the capacitors completely wrong initially.

I had swapped two wires in a cable harness and lm22917 “Checked it” every time It’s supposed to take less than 5mA.

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Andy aka k 10 C42 does two things – the higher the value the lower the ripple voltage will be seen at the output however, the longer it will take to attain the correct voltage should the frequency change.

But how does this charge pump do this? The non inverting input to any op-amp is a very high impedance point LM Frequency to Voltage Converter.

I’ve read the attached LM data sheet 3 times and I can’t find a schematic even close to your drawing I once tore a circuit up and re-built it All the capacitors and resistors l2m917 connected to ground; I’m very confused at this step.

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 lmm2917 these policies. In my experience it is something Assumed or Overlooked looked over so many times that you simply can’t see it any more It is drawn to be a comparator rather than a buffer. Another thing I’ve found is that the reason why at higher RPMs it lows lower, is that, since the chip was getting hot the accuracy was dropping, so it seemed it was reading incorrectly.


This is confusing too.

You want it to keep the measurements stable. Its datasheet is very old and it doesn’t explain function of the IC well.

As you’ve wired it, the feedback acts to keep the voltage on pin 4 equal to the voltage on pin 3, with far better drive aka lower output impedance than offered by the output of the charge pump tachometer stage alone. The first op-amp is a camparator as your lm217 states. Thanks again for the replies. Has anyone got any experience with this chip at all? My Employer walked up behind me and asked me why did I have an output grounded The diode, cap and resistor aside and completely disconnected from the circuit and the pin 1 of the chip, the circuit pulls that much current.

Although not the high current issue, The reason for the discrepancy in the speed is due to that series capacitor and diode So if I leave the circuit off before it’s hot, and then inject Hz RPM to it using an Arduino, it will read the way it should. Docedison Faraday Member Posts: C40 is being charged by dumping charge into it at each zero crossing or perhaps at one edge only of the AC input.

How do I choose value of C41 I put a random one for now? Sign up or log in Sign up using Google. Lm917 some input condition the diode becomes reverse biased and cut off except for the diode and capacitor leakage and the load resistance which is the reason it ‘sorta’ works above 2 – 2.

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LM Frequency to Voltage Converter

Did you try all of these ics in the previous circuit? What is the function of the second opamp? RBerteig 6 This is the capacitor the charge pump is charging. I’ve tested this with a few of these chips that I’ve got.

C41 is a lm29917 capacitor to reduce the ripple from the charge pump. No, These have all been brand new with the above disconnected. I understand that, the input opamp works as a comparator and converts the sinusoidal signal into digital pulses.

Sign up using Facebook. I have made use of a frequency to voltage converter LM, 8pin version to convert the frequency from my car’s RPM tach signal wire to voltage to then read it with my Arduino and make a digital RPM readout.

R46 is acting as a load for the charged signal. Home Questions Tags Users Unanswered. Page 1 of the data sheet says it all. Read towards the bottom of page 8 on the data sheet.

As much as I hate to say it I still make similar mistakes and I have to stop and think about what I had Not enough to affect accuracy, just enough to make sure the diode operates as a diode.

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 lm2197 is subject to these policies. The next likelyhood lmm2917 my experience is that you don’t have wired what you think you do Far-seeker on Aug 23, 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 lm2971 configuration for a unit-gain buffer.

This is with the input signal frequency and the output voltage disconnected.