This paper presents a stimulator for a cardiac neuroprosthesis aiming to restore the parasympathetic control after heart transplantation. The stimulator is based on time-to-current conversion, instead of the conventional current mode digital-to-analog converter (DAC) that drives the output current mirrors. It uses a DAC based on capacitor charging to drive a power efficient voltage-to-current converter for output. The stimulator uses 1.8 V for system operation and 10 V for stimulation. The total power consumption is I_stim×10 V+18.4 μW during the biphasic current output, with a maximum I_stim of 512 μA. The stimulator was designed in CMOS 0.18 μm technology and post-layout simulations are presented.