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Low Power Techniques

Low power design is a collection of techniques and methodologies aimed at reducing the overall dynamic and static power consumption of an integrated circuit (IC).

The higher the voltage, the higher the power consumed by each component, resulting in higher overall power. Conversely, the lower the voltage, the lower the overall power.
Dynamic power in circuits refers to the power consumption that occurs due to the charging and discharging of capacitors and the switching of transistors in digital circuits
Static power, also known as leakage power, is the power consumed by a circuit even when it is in a static or quiescent state, with no switching activity.

Dynamic : when the transistors in ON state

There are two types of dynamic power:

1. Switching power is the current that flows from the source voltage to the output capacitance and back to the ground.

2. Short circuit power occurs when current flows from the supply voltage to the ground when both NMOS and PMOS are active

The Need for Low Power Design

Nowadays there are new features and functionality, all packed into portable, handheld, and battery powered devices being used everywhere. For such products, improving the battery life by minimizing power consumption is an extremely important factor.
Improving the time it takes for a device to go from OFF/SLEEP state to ON/ACTIVE state is just as important, as with longer battery life.
For “plug-in” products, power consumption affects the overall cost of systems by requiring heat sinks and elaborate cooling systems, increasing electricity costs, etc.
So when massively parallel systems are used, a reduction in power for a single chip can result in significant power savings because it is used throughout the system. The power and cost savings by upgrading these systems with newer and more power efficient ICs can be significant.

Dynamic power saving techniques

This is a technique is used to reduce the overall dynamic power consumption of an integrated circuit.

Dynamic power reduction starts with planning appropriate voltage levels for various blocks in the design. The more work that the design is doing, the more energy it ends up needing.
As the speed to complete work in the design increases, the power required increases.
To save dynamic power, either you slow down the design (reduce clock speeds), try to reduce voltages, or attempt to cut down design activity.

Some popular dynamic power saving techniques include:

1. Clock Gating: This technique involves selectively stopping the clock signal to sequential elements when the data at the input of these elements is not changing, thereby reducing unnecessary switching activity.

2. Data-Gating: This technique involves selectively stopping the data signal to sequential elements when the data at the input of these elements is not changing, similar to clock gating.

3. Flop Cloning/Sharing: In this technique, the state of a flip-flop is retained and shared among multiple instances, allowing some flip-flops to be turned off when their state is the same as the shared state, thereby reducing dynamic power consumption.

Static power saving techniques

Static power saving techniques are employed to reduce the power consumption of an integrated circuit when it is in a standby or idle state.

These techniques aim to mitigate leakage losses, which represent a significant portion of power consumption in nanoscale circuits.

Some popular static power saving techniques include:

1. Low-power hardware components: This technique involves employing low-power hardware components to reduce the overall power consumption of the integrated circuit.

2. Hyper-threading: This technique involves enabling hyper-threading for logical cores to reduce power consumption.

3. Power Gating: Power gating techniques involve adding sleep transistors to the logic stack and employing feedback inverters to reduce leakage currents, thereby reducing static power consumption.

Difference between static and dynamic power management techniques

The difference between static and dynamic power management techniques lies in their approach to power optimization.
In the context of load management, static load management involves fixed charging rates for all electric vehicles (EVs) at all times, while dynamic load management adapts charging rates in real-time based on the grid's available capacity.
Dynamic load management offers greater flexibility and optimization, making it suitable for larger and more advanced EV charging networks with high demand. On the other hand, static load management is a cost-effective option for smaller EV charging networks with predictable and consistent demand.
In the context of computer science and integrated circuits, static power management techniques are invoked by the user and do not depend on CPU activities, such as a user-activated power-down mode. On the other hand, dynamic power management (DPM) techniques are automatic and depend on the CPU's activities for power optimization.
In the realm of integrated circuits, dynamic power management techniques focus on reducing power consumption based on the system's activity, such as reducing clock speeds, voltages, or design activity. This is in contrast to static power management, which does not depend on activity and is user-activated.
Therefore, the key distinction between static and dynamic power management techniques is that static techniques are user-invoked and do not depend on system activity, while dynamic techniques are automatic and depend on system activity for power optimization.

Dynamic power management techniques over static power management techniques

Dynamic power management techniques offer several advantages over static power management techniques, including:

1. Optimization: Dynamic power management techniques can optimize power consumption based on the system's activity, such as reducing clock speeds, voltages, or design activity. This is in contrast to static power management, which does not depend on activity and is user-activated.

2. Flexibility: Dynamic power management techniques can adapt to changing system conditions, such as workload or temperature, to optimize power consumption. This flexibility allows for more efficient power management and can lead to longer battery life in portable devices.

3. Cost-effectiveness: Dynamic power management techniques can be more cost-effective than static techniques, as they can be implemented using software-based solutions that do not require additional hardware.

Overall, dynamic power management techniques offer greater optimization, flexibility, and cost-effectiveness than static power management techniques.