An integrated digital buck DC-DC converter based on a 0.5µm standard CMOS process is presented in this paper. Its switching frequency is 5MHZ and no extra high frequency clock is needed. The delay-line ADC with a self-calibration loop utilized in the converter has low sensitivity to the process, voltage, temperature and loading (PVTL). The DPWM in the proposed DC-DC converter employs a first-order Σ-Δ modulator to achieve an equivalent resolution of 10-bit. The simulation results show that the proposed DC-DC converter can operate at the supply voltage range of 2.7 to 3.6V with a transient response time of 30µs. The peak efficiency reaches 94%.
A current-mode dc–dc converter with an on-chip current sensor is presented in this letter. The current sensor has significant improvement on the current-sensing speed. The sensing ratio of the current sensor has low sensitivity to the variation of the process, voltage, temperature and loading. The current sensor combines the sensed inductor current signal with the compensation ramp signal and the output of the error amplifier smoothly. The settling time of the current sensor is less than 10 ns. In the current-mode dc–dc converter application, the differential output of the current sensor can be directly sent to the pulse-width modulation comparator. With the proposed current sensor, the dc–dc converter could realize a low duty cycle with a high switching frequency. The dc–dc converter has been fabricated by CSMC 0.5-μm 5-V CMOS process with a die size of 2.25 mm $^{2}$ . Experimental results show that the current-mode converter can achieve a duty cycle down to 0.11 with a switching frequency up to 4 MHz. The measured transient response time is less than 6 μs as the load current changes between 50 and 600 mA, rapidly.
A novel current-sensing structure for current-mode DC-DC converter is presented in this paper. It has significant improvements on current-sensing speed and reducing the sensitivity to the variations of the process, voltage, temperature and loading (PVTL), which is derived in detail. It has been used in a current-mode DC-DC converter fabricated by CSMC 0.5μm CMOS process with a die size of 2.25 mm 2 . Experimental results show that with the current-sensing circuit the converter can operate at the supply voltage range of 2.7 to 5.5V with loading 0-600mA and has the ability to convert from 5.5V down to 0.6V at 4MHz. The measured transient response time is 7μs as the load current changes between 0 and 600mA rapidly. Moreover, the current-sensing structure can be also used in other integrated circuits for loop control and over-current protection.
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