| As more popular and powerful the portable devices are getting, personal information terminals, such as mobile phone and tablet pesnoal computer, are demanded high requirement, including more function, longer lifetime, smaller size and lower cost, among which longer using time is the most important one. Therefore, personal information terminal is judged mainly by the integrity of power management utility. In personal information terminal, the superiority of PMU maintaining relatively high efficiency over conventional chip power system is obvious. For its providing multiple power management functions, simple design, less external devices, higher integration. For those advantages, power management unit is a trend of the power solution in mobile portable device.For typical application of mobile device, this paper determines a PMU's design index and constructs the system and logic circuits. The PMU chip contains 200mA low drop-out voltage regulators (LDO) and four step-down converters, two of which realize output DVS through I2C. Considering the characteristics of analog circuit design in deep submicron process, digital assisted technology is introduced into the whole system and sub-blocks to improve efficiency and performance. Several important sub-blocks, including bandgap reference, digital to analog converter (DAC), 4 phase clock generator, are presented, analyzed, simulated in 0.13μm CMOS process under the help of Hspice with whole circuit and.layouted with Virtuso. After tape-out, the key parameters were tested and analyzed afterward.The testing results reveal that DVS function of the PMU works correctly; nearly no interface between different converters during power up and power down; programmable power-on sequencing is provided by connecting power good pin and en pin of each regulator to meet different applications requests; The peak efficiency of the DC-DC converters with outputs adjusted by resistors and I2C are 95% and 90%, which satisfies design index. |
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