Power management chip mc13892 Analysis

Source: Internet
Author: User

I. mx5x series uses Freescale mc13892 as PMIC. The schematic diagram pasted here takes the I. MX51 EVK board as an example.

Features features

1. battery charger system for Wall charging and USB charging
Battery charging systems include landline charging and USB charging.
2. 10 bit ADC for monitoring battery and other inputs, plus a Coulomb
Counter Support Module
The 10-bit ADC monitors the battery and other inputs, including a colon count module.
3. 4 Adjustable Output BUCK Converters for direct supply of
Processor Core and memory
4-channel adjustable step-down converter that directly powers the processor kernel and memory.
4. 12 Adjustable Output ldos with internal and external pass Devices
12-channel adjustable low-voltage differential linear voltage regulator.
5. Boost Converter for supplying RGB LEDs
A boost converter that powers RGB LEDs.
6. Serial backlight drivers for displays and keypad, plus RGB led
Drivers
Several backlight drivers for display and buttons
7. Power control logic with processor interface and event detection
Provides processor interface and event detection power control logic.
8. Real Time Clock and crystal oscillator circuitry, with coin cell backup
And support for external secure real time clock on a companion
System Processor IC
Real-time clock and crystal oscillator circuit, button battery can be used as a backup.
9. Touch Screen Interface
Touch Screen Interface
10. SPI/I2C bus interface for control and register access
SPI/I2C interface for control and register read/write.
11. Two package offerings in 7x7mm and 12x12mm
Two encapsulation methods: 7x7mm and 12x12mm

 

1. system modules

1.1 battery management, ADC and touch screen interfaces

In the figure, BP is the input pin and the power supply pin of the entire system. Using ADC for battery voltage, battery current, charging voltage, charging current, adin5 (can be used to detect battery temperature), adin6 (can be used to detect button battery voltage ), anin7 is used for detection.


1.2. Buck switcher)

Swxin is connected to BP, that is, power supply. The output voltage range of SW1 is 0.6v ~ 1.375, load current is 1050mA; sw2, sw3, sw4 output voltage range is 0.6v ~ 1.850, the load current is 800mA; the output voltage can be output by register configuration.


1.3. Low Voltage Regulator)

There are a total of 12 channels, which can be output to the corresponding external device; voltage settings can also be described in the corresponding registers. Detailed descriptions are provided in Chapter 7.3 of the manual.

1.4, backlight and three-color LED

The input and output directions on datasheet are incorrect. The output voltage can reach 26.5 V, and the maximum current output is 60mA. For three-color LEDs, each LED has eight current output levels. You can configure the relevant registers. For more information, see Chapter 1.

1.5, SPI and I2C Interfaces

You can use the SPI/I2C interface to access the registers and set them accordingly. You can use SPI or I2C.

1.6 logical interface and clock interface

We can see that there is 32 K clock input detection. When there is no 32 K clock source outside, the internal 32 K clock is used.
Two pumsx methods determine the order of power-on;
The Mode pin determines the mode in which mc13892 works. when the ground is connected, the normal mode (normal mode) works. When the vcore is connected, the test mode is enabled );
Pwronx can be used as the shutdown key;
The Int pin is the interrupt output pin of mc13892;
WDI is generally connected to the sw4 pin;
Resetbmcu and resetb are MCU reset pins and peripheral reset pins respectively;
Standby is the standby pin;
Clk32k is the 32 K clock output pin for peripherals;
Clk32kmcu is the 32 K clock output pin of the MCU. The vsrtc of the previous level supplies power to the 32 K clock output. clk32kmcu allows you to configure whether to output the clock;

 

2. system state machine

 

2.1. Off status

If the provided BP is smaller than the set threshold value (uvdet), no turn on event will be accepted;
If the provided BP is greater than the set threshold value (uvdet), The mc13892 core voltage and RTC start to work, and the remaining power supply is invalid, in this case, you can accept a turn on event to exit the off state.
The turn on Event mainly involves the following situations: power button press, charger attach, battery attach, and USB attach ), RTC alarm (RTC alarm) and system restart ).

2.2. Cold Start status
In this state, switchers and regulators will power on in sequence to prevent the influx of current. When it enters this status, reset timer starts to run. When the scheduled time is reached, resetb and resetbmcu will jump from low to high. At this time, the input control feet WDI and standbyx will be invalid.

2.3. watchdog status
In this state, mc13892 is completely under the control of SPI, and watchdog timer starts to run. When the time is reached, it will enter the on State. At this time, the input control scripts WDI and standbyx are still invalid.

2.4. On Status
Mc13892 can be completely controlled by SPI; WDI must be high. The recommended method provided here is to connect to sw4. If WDI becomes low, the system enters the off state or cold start;

2.5. User off Wait Status
Mc13892 can still be controlled by SPI. To enter this mode, you need to set the useroffspi bit to high to enter this mode. In this process, wait timer starts to run. When the scheduled time is reached, the user off mode or memory hold mode is determined based on the corresponding status bit.

2.6. Memory hold status
In this status, resetbmcu and resetb are low, and clk32k and clk32kmcu are invalid (of course, if DRM is set, clk32kmcu is still valid ). Set sw1mhmode = sw2mhmode = sw3mhmode = 0, sw4mhmode = 1;

2.7. User off status
Resetb is low, resetbmcu is high, and clk32k is invalid. If both clk32kmcuen and useroffclk are set or DRM is set, clk32kmcu exists. Sw1uomode = sw2uomode = sw3uomode = sw4uomode = 1; if you want to disable switcher, set the corresponding mode bit to 0.

2.8 warm start status
From this status, you need to wait for the scheduled clock to arrive;

The boot process should be: At the beginning, mc13892 is in the power supply state, and mc13892 is in the power-off state for the CPU. At this time, the core voltage of mc13892 and the RTC module are in the normal working state, at this time, the detection circuit will monitor the voltage changes of the power on/off pins. When the voltage rises, the rising edge will automatically perform a 30 ms shake, and it will recognize it as a turn on event, in this way, the default parameters of each regulator are loaded and started in order by default. The interval is 2 ms to avoid large influx of current;

Shutdown Process: The powr on/off key can also be used as the shutdown key. When the corresponding register bit is the relevant value, the key for 4s can enable mc13892 to power off the CPU, here, you should also modify the value of the reset register clock to prevent the system from restarting after shutdown.


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