What chip to convert 0-5V from sensor to pwm 0-100%
If you want a single device solution, the LTC6992 is a decent choice. There's a couple variants depending on required duty cycle range, so make sure you pick the right variant for your application. 

If that doesn't work for your needs, you might need to consider building it up yourself out of some discrete parts. There are many examples out there based around a 555 timer for doing voltage to duty cycle conversion.