naalald
Full Member level 4
Hello,
I have an oscillator/counter (74HC4060) which is part of a 100%-properly-working board. The oscillator with the external resistors and capacitors, generates a 73.5 kHz pulse (pin # 9, which is CTC). I'm trying to copy this oscillator in another board and I'm using the exact R & C values on the reference board. What I get is a 78 kHz pulse. So, this is the first problem.
Then, I checked the datasheet to understand about the R & C values and how I should change them to get the 73.5 kHz. The datasheet says the oscillation frequency is given by the formula: fosc = 1/(2.5*R*C), but when I put the R & C values in the formula I get 120 kHz. So, this is my second problem.
1- Why do I get a different frequency from the reference board?
2- Why does the oscillation frequency of the reference board differs from what the datasheet says?
I'm attaching the circuit.
Thank you.
I have an oscillator/counter (74HC4060) which is part of a 100%-properly-working board. The oscillator with the external resistors and capacitors, generates a 73.5 kHz pulse (pin # 9, which is CTC). I'm trying to copy this oscillator in another board and I'm using the exact R & C values on the reference board. What I get is a 78 kHz pulse. So, this is the first problem.
Then, I checked the datasheet to understand about the R & C values and how I should change them to get the 73.5 kHz. The datasheet says the oscillation frequency is given by the formula: fosc = 1/(2.5*R*C), but when I put the R & C values in the formula I get 120 kHz. So, this is my second problem.
1- Why do I get a different frequency from the reference board?
2- Why does the oscillation frequency of the reference board differs from what the datasheet says?
I'm attaching the circuit.
Thank you.