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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R46 is acting as a load for the charged signal. I think the problem is my Internal Zener references. This is the capacitor the charge pump is charging. To help save hands, I hooked an LED up to the output signal.

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. I feel well past my depth trying to sort this out How are you pulsing the 14V?

The sig-in line goes from 5. Then put a 10K resistor to the cathode of D3 and the other end of it to ground. An example circuit from the datasheet. How do I choose value of C41 I put a random one for now?

By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. I’m not game to hook it to my ‘duino nor can I be buggered going out to the bike yet Post as a guest Name. But how does this charge pump do this?


Yeah – I figured that i needed a decent ‘frequency’ The LM’s datasheet is at http: Page 1 of the data sheet says it all. I created a custom library for this IC and set up my own circuit as seen in the schematics above. I’ve built this on a breadboard using a modified version of http: You have fixed Pin 11 at about 0.


All the capacitors and resistors are connected to ground; I’m very confused at this step. I’m hoping someone can take a moment to help me and possible restor my sanity! I would take pin 1 and bias it with two 20K or so resistors going to supply and ground.

Since the chip was originally built to post-process a magnetic pickup for tachometer applications, the zero crossing would be easy datsaheet arrange for by directly wiring the pickup coil across pins 1 and 8.

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 datasyeet frequency falls. 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.

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National Semiconductor

Ideally, you’re going to need 8 pulses per second minimum, would be better for test purposes. The charge pump is charging a capacitor which one?

You want it to keep the measurements datasyeet. Im guessing now totally that my ‘test powersupply’ is putting 70ma across the base of thewhich is saturating it.


National Semiconductor – datasheet pdf

I’ve substantially edited this text to make it more true, see the edit history to see my incorrect babbling if you really want to. Home Questions Tags Users Unanswered. Sign up using Facebook. I think you problem lies with the input circuitry of the LM What is the function of the second opamp? 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.

Pin 11 and Pin 1 are the two inputs of a voltage comparator. It just gives several example l2m917 and a formula for the output voltage. I’ve played around with a few variations.

LM Datasheet(PDF) – National Semiconductor (TI)

Datasheeet is confusing too. Its driving me nuts However you have no DC biasing on Pin 1 so it will just swing about with the AC coupled input and not do anything. Checkout my projects development blog SLiDA. I want to learn working principle and internal circuit of the IC, and function of externally connected components especially C The first op-amp is a camparator as your question states.

I have then used the datasheet as well lm29177 this schematic to convert to 14 pin Email Required, but never shown. C40 is being charged by dumping charge into it at each zero crossing or perhaps at one edge only of the ,m2917 input. I understand that, the input opamp works as a comparator and converts the sinusoidal signal into digital pulses.

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