I have an application where I would like to derive a secondary square wave from a primary one but with a continuously variable phase shift. I would like to know if this is possible to achieve in a relatively simple manner, ideally without an FPGA or Arduino etc. I'm open to the idea of a PLL chip if these are approximately as inexpensive as, say, 741s or 555s and that the implementation does not imply a long settling time. However, if there is absolutely no other way of doing it then I'm open to more complicated suggestions.

The specifications for the primary square wave are not yet set in stone but the following can be taken as guidance:

* fixed frequency at some convenient rate (say 1MHz)
* 50% duty cycle
* 0-5V or 0-3.3V p-p or similar to suit any logic requirements

Specifications of the secondary derived square wave:

* phase shift from primary of 0-360 degrees
* not discrete steps but continuously variable (analogue control eg potentiometer, voltage input or similar)
* ideally an instantaneous phase shift (minimal settling time)

The other question ([Phase Shift Square Wave](https://electronics.stackexchange.com/questions/292711/phase-shift-square-wave)) with the same title as this one is different in that the OP wanted to produce 6 x 60 degree fixed sub-multiples of his original frequency. I want to be able to vary my shift continuously over one full cycle.