12-bit High-Voltage Current-Steering-Assisted R - 2R DAC With RCM and Parallel Switch for Satellite Applications

This work presents radiation hardened by design (RHBD) on a high-voltage (HV) digital-to-analog converter (DAC). A 12-bit HV DAC aiming at satellite applications is configured as a current-steering-assisted R- $2R$ ladder with common-level control resistors and parallel switches. The DAC structure employs current sources to mitigate the total ionizing dose (TID) sensitivity from switch resistance in a conventional R- $2R$ ladder. PMOS current sources and polysilicon-based R- $2R$ networks are utilized to avoid TID-induced leakage. Common-level control resistors are introduced to increase voltage headroom for the current sources. To reduce single-event effect (SEE)-induced bit-flip in control signals, a parallel switches scheme in every unit current source is proposed. An on-chip amplifier facilitates current-to-voltage conversion and output driving. The chip, manufactured in a 0.35- $\mu $ m HV CMOS technology, occupies 2.97 mm2. The TID test was conducted in two phases [up to 116 and 226 krad(Si)] with a Co-60 source. After being exposed to irradiation, the DAC exhibits less than two least significant bit (LSB) of integral nonlinearity (INL) degradation at 116 krad(Si) and then recovers to within 1 and 1.5 LSB from preirradiation at 116 and 226 krad(Si) of the total dose, respectively, after 24 h of room-temperature (RT) annealing. An SEE test with 20 min of 100-MeV proton irradiation shows no evidence of bit upset or fluctuation at the DAC output nodes.