NE555: Do you have any schematice for using NE555 as VCO?

Kazuya Nakai,

Figure 20 in the data sheet shows a VCO circuit. Pin 5 is the modulation input. The output frequency changes with pin 5 voltage. higher pin 5 voltage is lower output frequency. Duty cycle will also vary with pin 5 voltage.

Do you have a frequency range (span) in mind?

Ronald,
Thank you very muc for your prompt reply. I understood that.
The customer wants to control the output frequency between 0Hz and 3kHz.
Also they want to know how much the frequency accuracy roughly. Could you please give me any comment if you have idea?

Thank you again and best regards,
Kazuya Nakai.

Kazuya,

I will try to get this frequency range. Repeatability should be good. Linearity will not be very good.
Expect answer by end of week.

Ronald,

I'm looking forward to seeing your next reply.

Thank you and best regards,
Kazuya Nakai.

Kazuya,

This circuit should work from 0 to 3 kHz as pin 5 goes from 5V down to 0.5V (VCC = 5V)

I simulated this with similar TLC555 model which doesn't output correctly for pin 5 near 5V. However, in real device I don't believe that will be the case for NE555 (or even TLC555). I might be able to test this circuit next week.

NE555 0 to 3kHz.TSC