An 8-bit analog-to-digital converter based on a voltage-controlled oscillator using 180 nm CMOS technology from Mikron JSC with a supply voltage of 3.3 V for the analog part and 1.8 V for the digital part is presented. The analog-to-digital converter has a wide range of input voltages from 0 to 3.3 V. The transistor-level simulation of the analog-to-digital converter in the time domain was performed in Cadence Virtuoso. The sampling rate was set to 1 MHz. The power consumption is about 1.8 mW. The dimensions of the designed layout are 103 μm by 109 μm. With an input frequency of 50 kHz and an amplitude of 1.55 V, the post-layout simulation shows an output SNDR of 36.48 dB (ENOB is 5.77 bits).