I have a debouncing circuit using the MC14490. It is not working, and I am looking for some help in interpreting the datasheet.
In the datasheet, the active input should have a pull-up resistor, with the switch connected to ground. The oscillator input and output should be connected with a capacitor. I have the MC14490 connected up as shown in the datasheet, but when I close the switch a) the input pin does not go Low, and b) the output pin also does not go Low but c) the low side of the pull-up resistor does go Low (and the circuit works if I connect it up without the MC14490).
My Vdd is 3.3.V. I am using a 101 100pF capacitor to connect the oscillator input and output, and I have confirmed with a probe that the oscillator is working.
In the datasheet, the IC is described as 3 V-18 V, but all the switching values are give at 5, 10 or 15 V. At 5 V my 100pF capacitor would give a frequency of 15 KHz if I have read the datasheet correctly.
My questions are:
In the datasheet, the active input should have a pull-up resistor, with the switch connected to ground. The oscillator input and output should be connected with a capacitor. I have the MC14490 connected up as shown in the datasheet, but when I close the switch a) the input pin does not go Low, and b) the output pin also does not go Low but c) the low side of the pull-up resistor does go Low (and the circuit works if I connect it up without the MC14490).
My Vdd is 3.3.V. I am using a 101 100pF capacitor to connect the oscillator input and output, and I have confirmed with a probe that the oscillator is working.
In the datasheet, the IC is described as 3 V-18 V, but all the switching values are give at 5, 10 or 15 V. At 5 V my 100pF capacitor would give a frequency of 15 KHz if I have read the datasheet correctly.
My questions are:
- What would be a "typical" value for the oscillator capacitor in a 3.3 V circuit?
- What do the "typical" and "max" oscillator values mean? Do they mean that a frequency of 2.8 MHz is typical and a frequency of 1.4 MHz is the Maximum (minimum?)?
- What does the statement on page 6 mean: "Because of the built−in pullup resistors, the inputs cannot be driven with a single standard CMOS gate when VDD is below 5 V."