What is the PMIC in the phone

PMU as Consumer electronics (mobile phones, MP4, GPS, PDA, etc.) specific main chip matching power Management Integration Unit, can provide the main chip required, all, multi-grade and different voltage of the power supply, The same voltage energy supply different cell phone work units, such as processors, RF devices, camera modules, etc., so that these units can work properly. Integrated Power Management , charge control, and switch control circuitry as required by the main chip. Includes an adaptive usb-compatible PWM charger, multi-channel DC-DC Converter (Buck-DC Converter), multi-route regulator (LDO), Charge PUMP,RTC Circuit, Motor Drive Circuit,LCD backlight driver circuit, keyboard backlight driver circuit, keyboard controller , voltage/current/temperature, multi-channel 12-BITADC, and multi-channel configurable Gpio. protection circuits such as over/under voltage (OVP/UVP), over temperature (OTP), overcurrent (OCP) are also integrated. Advanced PMU distributes power safely and transparently between USB and external AC adapter, lithium battery and application system load. Dynamic Power Path Management (DPPM) shares the AC adapter current between the system and the battery charge, and automatically reduces the charge current as the system load increases. Adjust the charge current and system current distribution relationship to maximize the system's normal operation, when charging via the USB port, if the input voltage drops below the threshold to prevent the USB port from crashing, the input current is reduced based on the input voltage dynamic Power management (IDPM). The Power path architecture also allows the battery to compensate for such system current requirements when the adapter is unable to provide peak system current. 
The Ldo is a regulated device that uses a lower operating pressure differential to adjust the output voltage by negative feedback to keep it constant. Low pressure differential with Ldo, with a power-off function for easy management. The difference between the pressure and the high- DC efficiency. according to the system needs to provide a variety of voltage supply, these voltages are required for voltage adjustment, in addition, these power supplies can also be synchronized with the function on and off these supply voltages to support voltage domain switching. 
PMU is usually customized with the main chip binding. Because it's going to fit the CPU's power-up sequence. The power-up sequence of some voltages and the time interval between them have a succession relationship and a time requirement. The mask is good. PMU is actually a dedicated power controller with a mask program. To 32.768KHz crystals and 19.2M crystals. The standby state is 32.768KHZ crystal Work, the normal work is 19.2M of the main crystal work. 
on the battery after the pmic into the standby state , PMU by the 32.768KHZ Crystal to provide the clock, press power button trigger boot, install the customized boot sequence will be corresponding to the LDO,DC-DC open, 19.2M master clock work, After the CPU power is normal, the output is set to the CPU, the output reset signal to the CPU, release the reset signal, the CPU starts to start. The CPU output ps_hold signal will state the pmic in a working state. (The CPU will ps_hold when it shuts down and the pmic shuts down into the shutdown state.)
after the CPU is working properly, each module of the pmic can be controlled via the I²c interface. For example, when the system frequency conversion, the different operating frequency to adjust the core voltage to the corresponding voltage. RTC Time setting and alarm clock. At the same time, the pmic can generate an interrupt signal for the abnormal event to CPU,CPU and then interrupt processing. 
The more power supply to the pmic, the finer the power supply to the system, and the smaller the supply of each module, the more electricity is saved. 

What is the PMIC in the phone