PMIC power management

original text ：https://www.cnblogs.com/humaoxiao/p/4267614.html

exynos 4412 Power management chip PMIC Configuration and usage of
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• @author Maoxiao Hu
• @version V1.0.0
• @date Feb-2015

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• < COPYRIGHT 2015 ISE of SHANDONG UNIVERSITY >

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This article will improve and correct some minor mistakes from time to time , Be sure to go to http://www.cnblogs.com/humaoxiao Refer to the latest version .

Development board ： Xunwei 4412 elite .
uboot：uboot-2014-10.
PMIC：SAMSUNG S5M8767A

     In porting the new version u-boot When , Search the Internet for information on how to use the power management chip , It turns out that there's almost no , Even if it is datasheet It's also hard to download , I don't know why ？ I can only understand that this part of knowledge is relatively simple , No one wants to write . But make a note of how it works and how it works , There's no harm in the end . Another thing that still needs to be stated in advance is , Only the configuration method recommended by the official manual is provided here , Free play doesn't guarantee feasibility and stability .

One 、 overview
LDO and BUCK The concept of ： Please refer to 《 In embedded circuits BUCK VS LDO》.
S5M8767A Yes 9 road BUCK and 28 road LDO, For the time being, it can be regarded as common ownership 37 Three way power supply circuit . this 37 The lowest power supply circuit can be used 6.25mV Step voltage of , As many as 60 The output voltage can be precisely controlled by multiple voltage ranges . in addition S5M8767A There's also a hardware RTC, The clock information can be saved with external battery power supply .
Two 、PMIC And uboot The relationship between
uboot Initialize hardware by module , It has its own code order , This requires that PMIC Provide power to specific hardware in advance at a specific point in time , In order to offer uboot Do initialization configuration . otherwise uboot The execution of the law is bound to fail , for example PMIC Need to be in eMMC Before initialization, power the two power supplies .
in addition PMIC The initialization time of is uboot There's a default point in time , But this time point is closely related to the actual circuit of the core board and the bottom board , Need to advance or postpone according to actual needs .
2.0 PMIC in BUCK And LDO The classification of
PMIC Medium BUCK and LDO They can be divided into two kinds ：
One is PMIC Power on can directly output voltage BUCK and LDO.
The other is PMIC Power on does not output voltage , Need to use i2c Yes PMIC The output voltage can be set after configuration BUCK and LDO.
2.1 PMIC And DDR The relationship between
about 4412 Speaking of ,DDR The initialization of is in BL2 In the , If you use assembly to initialize the hardware i2c Come on PMIC It doesn't make sense to configure yourself , therefore DDR Your power needs to be connected to PMIC Default ON Of BUCK On , namely PMIC Power on can directly output voltage BUCK, No code configuration .
S5M8767A Recommended BUCK5 As DDR The power supply ,
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however ,BUCK5 The default output here is 1.2V,DDR What's needed is standards 1.5V, What's the problem ？
Samsung has long considered this issue for us , In order to adapt to different types of DDR,BUCK5 Can pass K9 K10 Level matching of two pins , Output four default voltages ：

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ad locum , Xunwei's development board is set like this ：

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thus ,B5S1:B5S2 = 1:0 namely BUCK5 Output 1.5V voltage , Coincide with DDR In line with the needs of .

2.2 PMIC And 4412 The relationship between the main chip
to ARM The core supplies the voltage PMIC Of BUCK2,BUCK2 Also by default. ON Of , Default output 1.1V. After consulting 4412 spec after , It should be noted that , stay 1.1V Under voltage , to ARM The core provides APLL The maximum output is 1000MHz, That is, if it is not set when the power is just turned on PMIC,ARM The core can only work in 1000MHz, Can't use the highest frequency 1.4GHz.

3、 ... and 、PMIC How to set it up
3.1 Communication protocol
S5M8767A Use I2C Deal with the 4412 communicate , The slave address is divided into two parts ,PM（Power Manager） and RTC, in other words PM and RTC The register addresses of are separate , It can be seen as two separate chips .

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3.2 give an example
With BUCK1 Give an example to illustrate the register setting method , Other BUCK and LDO similar , Read the manual carefully when necessary ：
BUCK1 There are two 8 Bit control register ,

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    CTRL1 It's low 6 Bit can be set according to the default value , The senior two need to explain ,00 and 1x There is no need to explain the meaning of ,01 It means  BUCK1 The switch is made by PWREN External pin control , And this PWREN Pins are generally associated with 4412 Of XPWRRGTON The pins are connected together , This XPWRRGTON By CPU Automatically controlled ,CPU In dormant state, this foot is low , This foot is high in working state , That is to say CPU Once out of hibernation ,PMIC It's going to give all of you PWREN The control of the BUCK & LDO Access to electricity .

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    CTRL2 It's control BUCK2 The output voltage of ,6.25mV Step value of , How much voltage you need to calculate by yourself and then write it .

Four 、 Quote from the experts PMIC Technical stickers
Originally written in ：《 What is? PMU》
－－－－－－－－－－－－－－－－－－－－－－ Reference start －－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－
What is? PMU（PMIC）
PMU（power management unit） It's the power management unit , A highly integrated 、 Power management solutions for portable applications , That is to say, several kinds of traditional discrete power management chips , Such as low dropout linear regulator (LDO)、 DC to DC converter (DC/DC), But now they're all integrated into the power management unit of the phone (PMU) in , This can achieve higher power conversion efficiency and lower power consumption , And fewer components to accommodate reduced board level space , A lower cost .
PMU As consumer electronics （ mobile phone 、MP4、GPS、PDA etc. ） Power management integrated unit for specific main chip , It can provide what the main chip needs 、 be-all 、 Multi grade power supply with different voltages , The same voltage of energy supply different cell phone work unit , Like a processor 、 RF devices 、 Camera modules, etc , Make these units work properly . Power management is integrated according to the needs of the main chip , Charge control , Switch on control circuit . Including adaptive USB-Compatible Of PWM The charger , Multi channel DC / DC converter (BuckDC-DCconverter), Multiple linear regulators (LDO),Charge Pump,RTC circuit , Motor drive circuit ,LCD Backlight driving circuit , Keyboard backlight driving circuit , Keyboard controller , voltage / electric current / Temperature, etc 12-BitADC, And multiple configurable GPIO. In addition, it has integrated / Undervoltage (OVP/UVP)、 Over temperature (OTP)、 Over current (OCP) And so on . advanced PMU Can be in USB And external AC adapter 、 Safe and transparent power distribution between lithium battery and application system load . Dynamic power path management (DPPM) Sharing AC adapter current between system and battery charging , And automatically reduce the charging current when the system load rises . Adjust the relationship between charging current and system current distribution , Ensure the normal operation of the system to the greatest extent , When passed USB When the port is charging , If the input voltage drops to prevent USB Below the threshold of port crash , Dynamic input voltage management is based on (IDPM) It reduces the input current . When the adapter is unable to provide peak system current , The power path architecture also allows the battery to compensate for such system current requirements .
LDO Is to take advantage of the lower working pressure difference , A voltage regulator that adjusts the output voltage through negative feedback to keep it constant . If the pressure difference is small, use LDO, With turn off function, convenient for power management . The big pressure difference is still used DC-DC Efficient .
According to the system needs, it can provide a variety of voltage power supply , These voltages are required for voltage regulation , In addition, these power supplies can be turned on synchronously with the functions 、 Turn off the supply voltage , To support voltage domain switching .
PMU It's usually customized with the main chip . Because it has to cooperate with CPU The power on sequence of . The power on sequence and time interval of some voltages have sequence relation and time requirement . This is a mask. OK .PMU It's actually a special power controller with mask program . want 32.768KHZ Crystal and 19.2M The crystal of . Standby mode is 32.768KHZ The crystal works , Normal work is 19.2M The main crystal works .
On the battery PMIC Enter standby mode ,PMU from 32.768KHZ The crystal provides the clock , Press POWER Press the key to trigger the power on , According to the customized boot order, the corresponding LDO,DC-DC open ,19.2M The master clock works ,CPU After the power supply is normal , The output is set to CPU, Output reset signal to CPU, Release reset signal ,CPU To start .CPU Output PS_HOLD The signal will PMIC The state of being at work .（ When it's turned off CPU take PS_HOLD Pull down the power ,PMIC Turn it off and turn it off ）
CPU After working properly , Can pass I2C The interface of PMIC Each module of the control system . For example, when the system changes frequency , Different working frequency should be adjusted core Voltage to the corresponding voltage .RTC Time setting and ALARM The clock of . meanwhile PMIC It can generate interrupt signal for abnormal events CPU,CPU And then interrupt processing .
PMIC The more power you have , The finer the power supply to the module of the system , The power supply of each module is less affected , So the more power you save .