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Simulation of Voltage Scaling for Dynamic Power Reduction

Comments(0)Filed under: thermal, low-power, power, low power, voltage, shutoff, MSV, AVS, CPF, DVFS, simulation, IR drop

This posting is part of a series of blogs on dynamic power management in digital-centric mixed-signal verification environments. In this post, I'll discuss the simulation of closed-loop voltage scaling for adaptive dynamic voltage and frequency scaling (DVFS).

My previous blogs covered some of the following topics:

        1. Basics of dynamic power management
        2. Very brief introduction to RNM (Real Number Modeling) for efficient simulation of mixed signal SoCs
        3. How to create a controlled voltage source using a Specman testbench
        4. Closed-loop voltage scaling

Previous postings include:

Simulation of Closed Loop (Adaptive) Voltage scaling

In this example, there are dedicated LDOs: ldo_mcu and ldo_dsp are modeled as wreal data types, supplying regulated voltage to two seperate power domains. The operating voltages are defined in the wreal models of the LDO and individually configured from the verification environment. Voltage transitions are controlled by the power controller based on estimated processing needs that are task dependent.

A noisy battery voltage is supplied from the verification environment and controlled by the test parameters and supplied to the two LDOs. The LDOs independently regulate the supplied battery voltage to supply nominal voltages to each independent power domain. There are 5 predefined nominal voltages for each LDO, and the outputs are independently scaled under control from the power controller to supply the regulated voltage to each individual power domain.


Figure 1: Closed Loop Voltage Scaling

Voltage scaling is orchestrated by controlling the output of the LDO to supply a targeted nominal voltage independently for each power domain. Figure 1 shows how closed-loop voltage scaling is performed on the SoC. The power controller determines the voltage level at which each power domain needs to operate, and then fine-tunes the supplied voltage based on feedback from the hardware performance monitors (HPMs) to perform closed-loop DVFS.

The HPMs are strategically placed inside the SoC and measure the targeted performance for each design unit. They provide feedback to the power controller to increase or decrease the operating voltage in real time. These are also modeled using wreals. The delay parameters and update rates are programmable and controlled from the verification environment.

The results of simulating adaptive voltage and frequency scaling are illustrated in Figure 2.


Figure 2: Adaptive Voltage and Frequency Scaling

In the next blog posting, I will write more about error detection during voltage scaling.

Stay tuned for more...





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