The binary pulsar PSRJ2145-0750: a system originating from a low or intermediate mass X-ray binary with a donor star on the asymptotic giant branch?

It is shown that the 6.84-day orbital period and relatively high companion mass of the 16.1ms period binary pulsar PSRJ2145-0750 find a consistent explanation if the progenitor system consisted of a donor star in the mass range 1-6M_sun_ with an orbital period such that this star overflowed its Roche-lobe on the Asymptotic Giant Branch (AGB). The present system then resulted after a phase of Common Envelope (CE) evolution. Initial donor masses in the range 2.4-6M_sun_ are possible only if, in addition to the orbital gravitational binding energy, other energy sources are available for expelling the envelope. The post-CE remnants of donors in the mass range 4-6M_sun_ overflow their Roche lobes and continue to transfer mass at a near or super Eddington rate for of order 10^6^yrs. This provides a simple way to explain the rapid spin and weaK magnetic field of PSRJ2145-0750.