[time-nuts] DAC for OCXO disciplining

[Lifespeed]

I have been looking into all-digital PLL designs to discipline an OCXO, the
scope of which would of course include GPS, as well as other reference
sources.  A component of the block diagram would be the DAC converts the
digital control loop output for application to the OCXO tune port.  In order
to use such a circuit to improve Allan deviation, rather than degrade it,
concerns like step size, Differential Non-Linearity (DNL), and possibly to a
lesser extent voltage noise, are concerns.  Some thoughts that have occurred
to me are coarse and fine DACs, possibly sigma-delta or pulse width
modulation (PWM).  Or some combination of all the above.

Any suggestions on topologies and/or candidate parts?  One possibility for
fine tuning might be the AD5791.

Lifespeed