Let us consider the stored 1 state again, as shown in Fig. For the RHBD 10T memory cell, according to SEU physical mechanism, nodes Q, QN, and S0 are three sensitive nodes for this stored value.• If the sensitive node Q is flipped to state 0 by a charged particle, transistor N1 will be temporarily OFF, and the switch state of transistor P6 will be ON temporarily. However, the voltage of node S1 will be its initial state, because the size of transistor P1 is larger than that of transistor P6 (2.
1× larger). As a result, the voltage of node S0 is unchanged. Hence, transistor P4 will be always ON.
Finally, the voltage of node Q will be flipped to the initial voltage.• If the sensitive node S0 is induced to change the initial state by a radiation particle, both transistors P1 and P4 will be temporarily turned OFF, and the nodes Q, QN, and S1 will be unchanged due to capacitive effect. Therefore, transistor P5 will be always ON, and the voltage of node S0 will be restored.• When node QN is flipped, the switch states of transistors N2 and P5 will be temporarily turned ON and OFF, respectively, and then the voltage of node Q will be changed to 0 state. Hence, transistors P6 and N1 will be also temporarily turned ON and OFF, respectively. However, due to the larger size of transistor P1, the value of node S1 will be its initial value so that transistor P2 also remains its OFF state.
Therefore, the affected node Q will be pulled up to 1 state, and then transistor N1 willbe turned ON again, and node QN will be pulled down to 0 state.ConclusionA novel RHBD 10T cell in TSMC 65-nm CMOS process is proposed in this brief. Compared with previous hardened 10T memory cell, the proposed cell can recover an error in any one sensitive node. The simulation results present that the penalty introduced for the proposed 10T cell is the increased write/read access time that may affect its applications with high-speed requirements. However, when considering the constraints of the target applications, compared with other hardened memory cells, the proposed RHBD 10T cell can be regarded as a good choice for aerospace applications as it provides a good balance among performance, area, power, and reliability for memories working at radiation environment.
