1 Introduction
With the application of a large number of emerging data services, the power consumption of smartphones has been greatly improved, resulting in a significant reduction in standby time. In order to extend the standby time, the design of the built-in battery has become more and more popular. This is because half of the volume of the lithium battery is occupied by its structural parts. If the battery is built into the body of the smartphone, the volume of the structural parts of the lithium battery can be saved, thereby greatly increasing the battery capacity in the same or even larger volume. capacity. As a result, the capacity of the battery has indeed increased dramatically, and a new problem has arisen. If the smart phone has a software system card machine during the application process, how to perform a system reset operation?
Compared to the main function of the product, the mechanical reset device that releases the condition of the card is usually backward. To prevent accidental reset of the device, most manual reset buttons (if any) are hidden in the body. Since the reset button is difficult to reach, disassembling the battery becomes a very common solution. However, this approach not only makes the user less perceptible, but also increases the cost and can also damage the system, for example, to lose important data.
So, how do you perform a hardware reset of the system in a smartphone with a built-in battery design? This paper introduces a solution for hardware intelligent reset, which can not only realize intelligent reset of double-key long press in smart phone design, but also realize the intelligent scheme of single-button on/off and reset popular in smart phones.
2 The mechanism and hidden dangers of the on/off and reset of the smartphone application platform
In the mainstream platform of today's smart phones, there is usually an application processor (ApplicaTIon Process / Baseband, hereinafter referred to as AP) plus a power management unit (Power Management Unit, PMU for short) architecture, as shown in Figure 1.
Figure 1. Hardware architecture of AP + PMU in a smartphone
In this hardware architecture, a power switch pin is provided on the PMU to be connected to a mechanical switch on the body (hereinafter referred to as Power_Key).
When the mobile phone is in the power-off state, press Power_Key to pull the power switch pin of the PMU to the ground, which will start the PMU power-on process: the PMU starts the LDO to supply power to the AP, and sends a hardware reset signal to the AP. When the AP software system is started. After that, a PS_HOLD signal is sent back to pull the PS_HOLD pin of the PMU high, and it remains high during the working state; if the AP fails to raise the PS_HOLD pin for a certain period of time (Tpshold time), it indicates that the AP The startup fails, and the PMU automatically performs the power-off process. A relationship between the Power_Key and PS_HOLD signals is usually required, that is, the Power_Key signal must be kept low until the PS_HOLD signal is driven high by the AP, as shown in FIG. This is because if the AP power-on initialization fails and the PS_HOLD signal is not raised within the set time Tpshold, the Power_Key remains low to ensure that the PMU will be triggered to power up again, thus ensuring successful power-on.
When the system is in the power-off state, if the Power_Key is short-pressed, the PMU will trigger the power-on process. When the AP power-on is completed, the PS_HOLD signal will be pulled high—the PS_HOLD of the PMU regardless of whether the button is pressed or released. Both can be pulled up in time during the Tpshold time through R2/C1/R1, and there is no problem in system power-on. When the system is in the working state, if the Power_Key is pressed, the PMU will enter the power-off process because the PS_HOLD signal is immediately pulled low. At the moment when the button is released, the system may be in a certain process of power-off or power-on process, which may lead to unpredictable results of possible shutdown and possible system reset. This is unacceptable for product design, as shown in Figure 5. Shown. More importantly, with this design, the system can not achieve software shutdown function at all. Therefore, in this circuit design, Power_Key and S1 cannot be set together.
Figure 5. Timing of the on/off button and reset button in the hardware architecture of AP + PMU
In order to correct the PMU itself does not have a dedicated hardware reset input pin, but need to use the PS_HOLD signal to pull low to reset this defect, the new PMU began to introduce a special RESET_IN reset pin, allowing external circuits to reset through this pin hardware PMU. However, the problem still exists here is that the PMU specification requires that the on/off button and the reset button must be physically separated and cannot be set on the same button. The reset button needs to be hidden in the manhole on the body. A solution for single-button on/off and reset.
So, is there a hardware solution that combines the on/off button and the reset button to achieve an intelligent solution for single-button on/off and reset in smartphone design?
Light reflectors in China with resonable price and good quality,We hope to establish cooperative relationship with you.
Light Reflector,Aluminum Light Reflector,Street Light Reflector,Energy Save Light Reflector
Yangzhou Huadong Can Illuminations Mould Manufactory Co., Ltd. , https://www.light-reflectors.com