Improved DC/DC converter performance enables more power efficient mobile processors

The problem of excessive power consumption of mobile device processors can be improved by improving the performance of DC-DC power converters. DC-DC power conversion chips with lower transient response are less likely to produce fluctuations in output voltage, which helps mobile device processors operate at a stable low voltage, thereby achieving the goal of saving power.

Therefore, to ensure the performance that the processor can achieve, the DC-DC power converter usually needs to operate at a higher voltage state, rather than operating at the lowest possible voltage state as in the ideal state.

Therefore, when developing a processor, much effort put into designing to extend precious battery life may be wasted because the processor is driven by a substandard DC-DC power converter whose transient performance and accuracy may be inadequate.

Through the description in this article, we will see how a DC-DC power converter with good built-in transient performance can achieve better power saving for the power management IC (PMIC).

To ensure the normal operation of the processor, the voltage output power must be stable

Processor manufacturers spend a lot of time on the power circuitry of the processor to ensure that power consumption is minimized while performance is maximized. In some cases, the processor will adjust performance to match the lowest possible power, or even use dynamic mechanisms to adjust the core voltage based on the processor's capabilities.

The processor requires a minimum voltage to maintain correct performance. However, under normal operating conditions, the output voltage of the DC-DC power converter will vary due to many factors, such as component variability, the operating mode of the DC-DC power converter, and transient load factors.

This means that the output voltage of a DC-DC power converter usually needs to be marked with a positive/negative tolerance level to ensure the correct operation of the processor, and the output voltage level of the DC-DC power converter must operate within the minimum value plus the tolerance range as much as possible.

Therefore, if the processor can only maintain a certain performance at a certain voltage, the DC-DC power converter must operate at a higher voltage to account for voltage drops, lack of accuracy, and transient responses that are often forgotten or ignored.

Therefore, if the output performance of the DC-DC power converter can be optimized under transient loads, the processor powered by it can achieve maximum performance at the lowest power consumption. By examining the transient performance of the DC-DC power converter built into more advanced PMIC products, it can be found that these optimized performance can save a lot of battery life for several different operating modes.

As shown in Figure 1, an integrated power management subsystem can provide a cost-effective and flexible single-chip power management solution. It is specifically designed for a range of low-power portable consumer products, but is also suitable for any application with a multimedia processor. Manufacturers have launched PMICs that support ARM processors, but can also support most applications and core mobile processors for various low-power multimedia applications.

Figure 1 Highly integrated PMIC system circuit diagram

Integrated PMIC enables low-power processors

The DC-DC power converter BuckWise technology can provide 2.5A output current. It has various advantageous features such as programmable InstantConfig EEPROM boot program configuration, secure RTC, auxiliary analog-to-digital converter (ADC), low-power 32kHzRTC crystal oscillator, I2C and DVS interface. In addition to being fully customized, it can also produce highly efficient and scalable solutions.

On the other hand, the efficiency of the DC-DC power converter will change due to different operating conditions. Therefore, for a valid comparison, it is first assumed that the system power efficiency of the three test categories is 80%. The actual system efficiency will also be considered in the later analysis to show how the benefits of changing the DC-DC power converter mode will affect the battery life of the system.

As shown in Figure 2, under certain conditions, the transient response is ±6mV. Therefore, in theory, the voltage level applied to the processor will only be 6mV higher than the required voltage. Moreover, under similar conditions, other PMICs may have the opportunity to exceed ±30mV.

Figure 2 Transient response of DC-DC power converters 1 and 2 of a highly integrated PMIC under specific conditions

Since the power consumption of a processor is proportional to the square of the voltage, the increased power consumption can be easily estimated. This also means that the battery life will be significantly increased when using a DC-DC power converter with better transient performance.

Designers can optimize for different systems if they choose to use a PMIC with multiple operating modes. Table 1 shows the transient performance measurements of a DC-DC power converter in different operating modes under the same conditions as above.

This article shows how the transient performance of DC-DC power converters differs from traditional PMIC solutions in terms of power saving and battery life. A PMIC contains several DC-DC power converters. If we only look at a single DC-DC power converter, there are advanced technologies on the market that can extend battery life by 7.5% compared to a traditional PMIC with a transient performance of 30 millivolts.

Furthermore, this power saving does not require any circuit redesign or the addition of any components; it can be achieved simply by reducing the DC-DC power converter output voltage to the minimum value.