Achieving high operating temperature (HOT) plays a crucial role in miniaturizing type-II superlattice (T2SL) mid-wavelength infrared (MWIR) focal plane arrays (FPAs). However, their full potential has yet to be realized due to a lack of complete understanding of their operation from the perspective of detection principles. Here, by investigating the photon transmission path and optoelectronic performance of the simulated devices, a detailed noise equivalent temperature difference (NETD) model of the T2SL MWIR FPAs was established. The NETD limitations in the optics-limited and detector-limited modes were revealed by studying the effects of the source, optical system, and FPA-related parameters. Although NETD exhibits sensitivity to dark currents, improvements in the quantum efficiency and well capacity can further boost its performance. When the defects and carrier lifetimes are well controlled to completely suppress the dark current, the NETD of an MWIR system with optimized integration times, which operates between 150 K and 200 K, is predicted to be below 10 mK when detecting room-temperature targets. The results provide new insights into the model and sources contributing to the NETD and demonstrate the possibility of high-temperature operation of T2SLs MWIR FPAs.