Other Parts Discussed in Thread: OPA197, LF411
Good Day
I have been tryiing to understand the datasheet of the LM 331 specifically the Voltage to frequency converters. Several question have occurred to me as well as confusion.
1) On page 12, Figure 14 (Figure 14. Simple Stand-Alone V-to-F Converter with ±0.03% Typical Linearity (f = 10 Hz to 11 kHz) seems to be in conflict with the ranges given in section 9.2.1.1 - Design Requirements. The figure states Vin is 10V full scale and Fout as 10kHz. but yet in the design requirements it is stated that " For this example, the system requirements are 0.05% linearity over an output frequency range of 10 Hz to 4 kHz with an input voltage range of 25 mV to 12.5 V. " This seems to be in conflict with each other.
2) When i use the formula ƒOUT = (VIN / 2.09 V) × (RS / RL) × (1 / RtCt). By substituting the values from the diagram I get an Fout value of 10554,46102 Hz for a Vin of 12.5 V. This is not the 4kHz value which was required.
3) Does the supply Voltage have any effect on the circuit? so any Vs voltage within the range of 4 to 40 V shall produce near identical Frequencies?
4) The Rs value should always be atleast 12k to 16k to ensure that not too much current gets draw from the internal circuit. therefore to modify your frequency output only Rt and RL an be manipulated and should be the same?
5) The 5K adjust for Rs is that to cater for the component intolerances?
6) The current output from Pin 3 is relatively small (typically mA) therefore if more current is needed it should be used with a transistor or a buffer amplifier?
7) What is the 22K offset adjust? Is it a 22K potentiometer? Is it important?
8) My objective is to convert a 1-5 Volts signal into a proportional frequency. Then pass it through an optoisolator. Then convert it back to a voltage, using a frequency to voltage converter on the other end. Is this actually possible using the Lm 331 for both V-F and F-V conversions? Will It be relatively accurate?
9) Is the LF411CP op amp a good replacement for the LF411A op amp found in section 9.2.2 Precision V-To-F Converter. Page 14 figure 16 of the datasheet?
I thank you in advance for any help that I may receive.