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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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. Page 1 of the data sheet says it all. R46 is acting as a load for the charged signal.

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I’ve checked the current that the circuit takes and it’s about 65mA. The charge pump is charging a capacitor which one? At lm29117 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. I guessed the roles of the capacitors completely wrong initially. How do I choose value of C41 I put a random one for now? There is no discharge path for that 2R2uF cap This is with the input signal frequency and the output voltage disconnected.

By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. No, These have all been brand new with the above disconnected. As much as I hate to say it I still make similar mistakes and I have to stop and think about om2917 I had That schematic indicates they shouldn’t be, but with that style it would be easy to misread that. This is the capacitor the charge pump is charging. The resistor, capacitor and the diode connected to the tach signal wire is to get rid of the DC offset.

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The load is needed to convert the stored charge into a voltage that can be lm2971, and pragmatically to provide a place for the stored charge to leak off into as frequency falls. The data sheet provides the detailed arithmetic, but the telling point is that the relationship between input frequency and output voltage only depends on C40 and R Its datasheet is very old and it doesn’t explain function of the IC well.

I think Know you will find a negative voltage present on pin 1 when the chip gets hot Read towards the bottom of page 8 on the data sheet.

LM Frequency to Voltage Converter

The datasheet indicates a typical use case for the chip being to light a warning light when input om2917 exceeds a threshold, in which case having an output transistor capable of sourcing or sinking more current makes sense. Any help is appreciated.

Here’s a hand-waving explanation from llm2917 digital and software guy who has bumped in to sharp edges in the analog side I need a circuit which generates 1mV voltage per 1Hz frequency.

Andy aka k 10 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. An example circuit from the datasheet. There are 2 problems at the moment: I understand that, the input opamp works as a comparator and converts the sinusoidal signal into digital pulses.


Sign up using Email and Password. All the capacitors and resistors are connected to ground; I’m very confused at this step.

I have made use of a frequency to voltage converter LM, 8pin version to convert the frequency from my car’s RPM l2m917 signal wire to voltage to then read it with my Arduino and make a digital RPM readout. Sign up using Facebook.

C41 is a filter capacitor to reduce the om2917 from the charge pump. The first op-amp is a camparator as your question states. 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.

What happens, If you Ground pin 1, to the current drain But how does this charge pump do this? 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.

What is the function of the second opamp? Perhaps you have burned them all. I had swapped two wires in a cable harness and had “Checked it” every time It is drawn to be a comparator rather than a buffer.

It just gives several example circuits and a formula for the output voltage.