A 480-MHz, multi-phase interleaved buck DC-DC converter with hysteretic control

We propose an on-chip 1.8 V-to-0.9 V DC-DC converter aimed to reduce the input current and decoupling requirements of future microprocessors. By utilizing a 90-nm CMOS process, employing a four-phase hysteretic control, and operating at ultra-high frequency of 480-MHz, we achieved a 10% output droop with only 2.5 nF of on-chip decoupling, for 0.5 A of load current. No off-chip decoupling was connected to the output. At 480 MHz the measured efficiency was 72%. At 250 MHz, the efficiency improved to 76% at the cost of a 17% droop or larger decoupling of 11.5 nF. A converter with 100 A rating would require a capacitor of 0.5 μF, which is comparable to the size of an on-chip capacitor of a typical microprocessor.