A (0, G/I) code is a modulation code used in the PRML recording system in which G and / represent the maximum number of zeros between two consecutive ones in the global sequence and the interleaved subsequences, respectively. For some magnetic recording systems such as the one with a helical scanning rotary head, a de-balanced write waveform is required to meet channel requirements. In this study, charge-constrained (0, G/I; C) sequences which can generate a de-balanced write waveform are investigated, where C represents the upper bound of charge. Based upon the runlength subgraphs and the transition matrices, capacities and power spectra of (0, G/I; C) sequences are derived and computed. Index Terms- Capacity, modulation code, partial-response maximum-likelihood recording, runlength graph.