Simulating digital circuits numerically – a charge-oriented ROW approach

Abstract. A ROW type approach is considered for integral form DAEs arising in charge-oriented nodal analysis of digital networks. These network equations define very special index-2 systems that can be solved by Rosenbrock-Wanner (ROW) methods suitable for semi-explicit index-1 systems without order reduction. To obtain charge conservation, the charge variables are projected on the linear charge constraint. In contrast to the semi-explicit index-1 case, all order conditions for the algebraic variables up to order $p$ have to be fulfilled for a method of order $p$. CHORAL, an embedded charge-oriented method of order (2)3, is introduced and compared with DASSL and RODAS for two industrial applications, the NAND gate and the two-bit adding unit.