To solve the problem of narrow operating frequency of traditional adaptive on-time control DC-DC converter, an adaptive timing circuit for wide-frequency application was proposed. Based on the DC-DC converter with PLL modulation, the current of the oscillator was introduced into the timing circuit through a full CMOS current multiplier. The center frequency of the timing circuit could follow the frequency of the oscillator, so the adaptive on-time control DC-DC converter could work in a wide frequency range. The adaptive timing circuit was simulated by 0.18 μm BCD technology. The results showed that the frequency range of the DC-DC converter using the adaptive timing circuit was 0.27~3 MHz.