RHBD Bias Circuits Utilizing Sensitive Node Active Charge Cancellation

A novel radiation-hardened-by-design (RHBD) technique that utilizes charge sharing to mitigate single-event voltage transients is employed to harden bias circuits. Sensitive node active charge cancellation (SNACC) compensates for injected charge at critical nodes in analog and mixed-signal circuits by combining layout techniques to enhance charge sharing with additional current mirror circuitry. The SNACC technique is verified with a bootstrap current source using simulations in a 90-nm CMOS process. Reductions of approximately 66% in transient amplitude and 62% in transient duration are observed for 60-degree single-event strikes with an LET of 40 MeV*cm
²
/mg. The SNACC technique can be extended to protect multiple sensitive nodes (M-SNACC). M-SNACC is used to harden the bias circuit of a complementary folded cascode operational amplifier, providing a significant reduction in single-event vulnerability for a 8-bit digital-to-analog converter.