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
|Published (Last):||7 November 2005|
|PDF File Size:||1.21 Mb|
|ePub File Size:||12.20 Mb|
|Price:||Free* [*Free Regsitration Required]|
Then put a 10K resistor to the cathode of D3 and the other end of it to ground.
National Semiconductor – datasheet pdf
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 played around with a few variations.
R46 is acting as a load for the charged signal. Daatasheet is drawn to be a comparator rather than a buffer. I guessed the roles of the capacitors completely wrong initially.
LM Datasheet(PDF) – National Semiconductor (TI)
But how does this charge pump do this? The charge pump is charging a capacitor which one? This is confusing too. What is the function of the second opamp?
Sign up or log in Sign up using Google. How are you pulsing the 14V? Its datasheet is very old and it doesn’t explain function of the IC well. 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 I’m not game to hook it to my ‘duino nor can I be buggered going out to the bike yet I need a circuit which generates 1mV voltage per 1Hz frequency.
Read towards the bottom of page 8 on the data sheet.
I’m hoping someone can take a moment to help me and possible restor my sanity! 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 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.
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. Therefore to get the chip to do anything you have to take pin 1 above and below this point. 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 output transistor is provided with open emitter and collector to permit its use in a variety of configurations. 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.
This is the capacitor the charge pump is l,2917. Can anyone offer some guidance? Home Questions Tags Users Unanswered. I want to learn working principle and internal circuit of the IC, and function of externally connected components especially C C41 is a filter capacitor to reduce the ripple from the charge pump.
It just gives several example circuits and a formula for the output voltage. I feel datawheet past my depth trying to sort this out The LM’s datasheet is at http: Andy aka k 10 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.
And heres my breadboard datasheeg I think you problem lies with the input circuitry of the LM