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 had swapped two wires in a cable harness and had “Checked it” every time This is the capacitor the charge pump is charging. I’m trying to make a frequency-to-voltage converter by using LM It is drawn to be a comparator rather than a buffer. 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.

I need a circuit which generates 1mV voltage per 1Hz frequency. If you look at the series diode capacitor connection and think about it carefully you will see that at some input condition pulses in the cathode of the diode must go positive as the diode prevents the capacitor from discharging and at some point the diode is biased off Not enough to affect accuracy, just enough to make sure the diode operates as a diode.

Sign up using Email and Password. This is confusing too. Did you look at the data sheet I included? The output transistor is provided with open emitter and collector to permit its use in a variety of configurations. But how does this charge pump do this? 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. I’ve checked the current that the circuit takes and it’s about 65mA.

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C40 is being charged by dumping charge into it at each zero crossing or perhaps at one edge only of the AC input. An example circuit from the datasheet.

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. By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

Although not the high current issue, The reason for the discrepancy in the speed is due to that series capacitor and diode Did you try all of these ics in the previous circuit? I’ve read the attached LM data sheet 3 times and I can’t find a schematic even close to your drawing There are 2 problems at the moment: The data sheet provides the detailed arithmetic, but the telling point is that the relationship between input lm2971 and output voltage only depends on C40 and R Home Questions Tags Users Unanswered.

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In my experience it is something Assumed or Overlooked looked over so many times that you simply can’t see it any more RBerteig 6 Perhaps you have burned them all. Sign up using Facebook. 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.


A quick look at the datasheet suggests the diode on the input isn’t necessary, it seems desined to have l2m917 tach ac input, no experience with the ic tho.

LM Frequency to Voltage Converter

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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. The first op-amp is a camparator as your question states. Its datasheet is very old and it doesn’t explain function of the IC well.

I understand that, the input opamp works as a comparator and converts the sinusoidal signal into digital pulses. C41 is a filter capacitor to reduce the ripple from the charge pump. Thanks again for the replies.

Page 1 of the data sheet says it all.

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I’ve substantially edited this om2917 to make it more true, see the edit history to see my incorrect babbling if you really want to. If so the device is defective. What happens, If you Ground pin 1, to the current drain