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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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Andy aka k 10 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. Datashwet think you problem lies with the input circuitry of the LM The output transistor is provided with open emitter and collector to permit its use in a variety of configurations.

You have fixed Pin 11 at about 0. I would take pin 1 and bias it with two 20K or so resistors going to supply and ground. I have then used the datasheet as well as this schematic to convert to 14 pin Since the chip was datasneet 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.


I guessed the roles of the capacitors completely wrong initially. However you have no DC biasing on Pin 1 so it will just swing about with the AC coupled input and not do anything.

National Semiconductor

The datasheet indicates a typical use case datasheeg the vatasheet 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. Datashfet 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 All the capacitors and resistors are connected to ground; I’m very confused at this step.

Here’s a hand-waving explanation from a digital and software guy who has bumped in to sharp edges in the analog side This is confusing too.

I feel well past my depth trying to sort this out I think the problem is my Internal Zener references. I’m trying to make a frequency-to-voltage converter by using LM An example circuit from the datasheet. The charge pump is charging a capacitor which one?

Sign up or log in Sign up using Google. Sign up using Facebook. 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 l2917 stage alone. The sig-in line goes from 5. C41 is a filter capacitor to reduce the ripple from the charge pump.


Post as a guest Name. It just gives several example circuits and a formula for the output voltage.

I’m stuck with a pin LM – i’ve got an 8-pin on order now, but datsaheet it, I want to get this to work. Can anyone offer some guidance?

LM Datasheet(PDF) – National Semiconductor (TI)

L,2917 is drawn to be a comparator rather than a buffer. 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.

I’ve built this on a breadboard using a modified version of http: How do I choose value of C41 I put a random one for now? Its datasheet is very old and it doesn’t explain function of the IC well.

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