It′s the trend of information technology development that infrared focal plane array (FPA) outputs digital signal directly, the critical technique is the digital readout integrated circuit (ROIC). The architecture of digital ROIC was introduced in this paper after the summary of related research status. The sources and influence of temporal noise and spatial noise were analyzed in detail, then the design guide for low noise was also shown. In addition, two digital ROICs were designed based on the discussion of linearity, dynamic range and frame rate. The first ROIC was implemented with column-level ADCs, which was used for 640×512 digital FPA. The measurement results show that the readout noise of ROIC is 150 μV, and the NETD with mid-wave infrared detectors is 13 mK. Digital pixel architecture is used for the second ROIC, which is connected to 384×288 long-wave infrared FPA. The measured NETD is less than 4 mK, and the dynamic range is larger than 90 dB. The max frame rate achieves 1 000 Hz. The two ROIC prototypes effectively improve the sensitivity, dynamic range and frame rate of infrared FPA, which confirms the advantages of digital ROIC technology to the performance development of infrared detectors.