TL494 duty cycle control help!

[Manmash]

I'm using TL494 to generate PWM. the max duty cycle is 45% and i need 20% which i am struggling to obtain (datasheet is attached) .... according to the datasheet, I understood that The duty cycle can be controlled by adjusting the voltage on the feedback pin(3) ..... I keep getting the same output 5v, no matter what the voltage at pin 3 is ... wat am I doing wrong??

Any help is highly appreciated .............

MOD: Your attchment was the device datasheet which is found freely on the net. Do not upload anything what you get on the net. Instead a link to the file if mandatory is sufficient. Read rules / announcemnets to avaoid warnings.

 

[pranam77]

... wat am I doing wrong?? Any help is highly appreciated .............

Instead expecting members look at the device datasheet, you may upload your schematic where the PWM is implimented and expect better responses.

 

[leo_o2]

If you want to control duty cycle, you must disconnect the feedback loop. Just use open loop configure.

 

[easyamp]

One way to control dead time with tl494 is adjust the voltage going to the dtc pin(pin 4). 0v/Gnd on pin 4 is 45% duty and +3.3~+3.35 is 0% duty. The duty cycle is fairly linear in between 0 to 3.35 so some where in the middle of those is 20%. I use the dtc pin for over current and remote turn on so I can use both error amps for other stuff. A simple 10k pot divider network attached to pin 4 and using gnd and vref will get you a good stable adjustable duty cycle.