I am trying to configure my LM567CN to respond to frequencies of about 19kHz using the following formula: F = 1 / (1.1 * R1 * C1), but the chip responds to completely different frequencies. The datasheets I've found mention LM567 and LM567C. Is it possible that the formula will be different for LM567CN?
Yes that is what I also Calculate using that formula.
This is the Formula shown in my 1982, National Data Book.
I will prototype it a little later and check it out.
But Looking at the Data Sheet, QUOTE.
11.2.1.2.1 Timing Components
To calculate the timing components for an approximated desired central detection frequency (f0), the timing
capacitor value (C1) should be stated in order to calculate the timing resistor value (R1). Typically for most
applications, a 0.1-µF capacitor is used.
1.1
fo = -----
R1 C1
This is the Formula that is now shown in the Online PDF.
So, Which is Correct?
Do you use the output and loop filters mentioned in the datasheet?
I don't know what restrictions there are for the R value, but I think it should not be too low.
Try a few kohms for it.
Edit: I found a Philips datasheet, where R is recommended between 2 and 20 kohm
Do you use the output and loop filters mentioned in the datasheet?
I don't know what restrictions there are for the R value, but I think it should not be too low.
Try a few kohms for it.
Edit: I found a Philips datasheet, where R is recommended between 2 and 20 kohm
so that using the 1.1 / R1C1 formula, this should result in the centre frequency of about 19.3kHz.
However, the output at PIN 8 is always high. I tested it for frequencies between 10 and 24kHz.
Algebraically, your formula is no different than the TI formula. Did you miss that point?
I didn't mention before, because my purpose was to point out that there were two formulas from the two manufacturers. In theory, the multiplier could be changed depending on the comparator threshold set; however by analogy to the 555, I suspect the TI formula is the correct one.
Algebraically, your formula is no different than the TI formula. Did you miss that point?
I didn't mention before, because my purpose was to point out that there were two formulas from the two manufacturers. In theory, the multiplier could be changed depending on the comparator threshold set; however by analogy to the 555, I suspect the TI formula is the correct one.
If you can post your R1 and C1, and the centre frequency you got, I will try to replicate your exact values to make sure that there are no other issues with my circuit.
If you can post your R1 and C1, and the centre frequency you got, I will try to replicate your exact values to make sure that there are no other issues with my circuit.
I Used a .1 uf Cap but with Various Resistance Values and got Correct Frequencies on my Frequency Counter.
If you use a .01 Cap and a 5.8K resistor, you will come Close to your 19Khz.
Remember that Just because a Cap is Marked .01, Does Not mean it is that Exact Value.
Possibly use a 5K6 resistor in series with a 500 Ohm trimpot to Get the Exact Frequency of 19Khz.
Note the Supply Voltage MUST beRegulated at 5 Volts.
Or the Frequency will Change with Supply voltage changes.