Abstract: An on-chip frequency compensation structure for the current mode DC-DC converter is presented. With an integrated RC network, it realizes the loop frequency compensation and overcomes the drawback of stability dependency on load resistance due to the output ceramic capacitor’s low effective series resistance, which reduces the pin numbers, saves the PCB space and stabilizes the chip. Also the optimized feedback network makes the crossover frequency insensitive to the change of the output voltage, improving the load step response further. A DC-DC buck converter with a proposed structure has been fabricated with a 0.5 μm CMOS process for validation. The measurement results show good stability. Both load and line regulations are less than 0.4％. And the output voltage can be recovered within 8 μs for a 400 mA load step. The occupied PCB space is also reduced 14％.

Key words: DC-DC converters, current mode control, stability, on-chip frequency compensation