PWM with variable duty cycle on a chip?
>I am working on a project with a data acqusition board. I need the
>ability to send an analog voltage to a device (or devices) and be able
>to adjust the duty cycle of a PWM voltage from about 25% to 100%.
>I tried using a 555 timer, but it is somewhat unstable. Does anyone
>know of a device which will perform this function, or have any other
>methods to try?
After searching myself for a Voltage to PWM converter on a single IC,
that provided a 0% to 100% duty cycle adjustment and a BASE-FREQUENCY
greater than 25kHz with absolutely no luck (Hard part was the
BASE-FREQUENCY). The only thing I found even close from LINEAR
TECHNOLOGIES was a variable speed cordless drill driver with a
BASE-FREQUENCY of 5kHz.
I designed my own that will go from 0% to 100% with an input voltage
ranging from 0V to 5V and provides a BASE-FREQUENCY of about 31kHz on a
single IC. (Dual OP-Amp)
...There is also another version that I have that will operate down to
2.5V (BF=34kHz)that I haven't posted yet. If you are working with 3V
logic I can provide it to you. The above method (v2pwm.gif) fails to
oscillate at about 4.5V supply voltage.