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Energy consumption is an important parameter that not only concerns sustainability. It is true that by optimizing the use of energy on the device, less energy will be required to perform its function, therefore more efficient, but also by performing this optimization you will have an overall better product.
For example, if the product is battery powered then you can extend its battery life or even better reduce the size of the battery, lowering costs and reducing the embodied energy of the product. As with many things in life, optimizing power consumption in an electronic device follows the Pareto principle or rule. A distinction should be made between a battery and non-battery powered systems.
Some of these optimizations can drastically reduce the energy consumption of the device, such optimizations should be then applied to both battery and non-battery powered devices. It only makes sense to apply these optimizations for battery-powered systems, where that small fraction of current is actually relevant. At the end of the article, a comparison will be made between an optimized and non-optimized system hence the impact of the changes can be visualized.
In many embedded systems, the MCU will be one of the main culprits of high power consumption if left unchecked. MCU power consumption can be divided into two states: Dynamic power consumption is the current consumed during the normal operation of the MCU.
It includes the power lost in switching the internal CMOS transistors that normally control functions such as the digital output and other MCU circuits like the ADC modules and the clock oscillator. However, if we analyse it dynamically, during the transitional states from Vcc to GND and vice-versa, the capacitor charges and discharges, hence power is wasted. By looking at the previous equation, we can see that the most important variable regarding consumption is the MCU is voltage.
For that reason, it is a better option to choose a lower voltage MCU. If not required by your application, try to avoid powering your MCU with 5V. Another parameter is the external capacitance. Anyhow, if you have a high-speed signal connected to that pin such as an SPI clock, you cannot put a big capacitor as you will over damp the signal make the square wave a curvy squared wave and the communication between the devices will not work.
Regarding the frequency, initially, it seems that by having a lower switching frequency there is less power consumption. However, you must fact into account that by having a lower switching frequency the component will also take longer to finish the task, therefore consuming current from another part.
As we will see later, it is more efficient to finish quickly the task and then enter into low power mode. Static power is the power consumed by the MCU while this is not actively running code, therefore in sleep or low power mode. The current consumed in this state is drawn mainly by quiescent currents from the internal voltage regulator, BOR circuit and internal oscillators.
Also, some current is lost from leakage. Running the clock itself will consume more current. However, it turns out that the initial current required to power the oscillator represents a significant portion of the total power consumption at low frequencies, on the other hand, at high frequencies it becomes negligible. Bear in mind that for this principle to apply, the oscillator must be powered by a low impedance voltage source that can quickly deliver the required current.
When choosing the clock speed of peripherals there are two variables to take into account: Therefore, it is more beneficial to use a high current peripheral that takes less time to perform the task. Internal circuits of the ADC are mainly analogue components that do not vary its consumption with speed. Because most of the current consumption of the ADC comes from powering these components, it is more beneficial to have a high-speed conversion and then disabling the module.
This circuit can consume a considerable amount of current while in sleep or low power mode. For that reason, it is better to turn it off while the MCU enters into this state. Unused pins 7805w are left floating, can couple with an external signal and produce a random voltage which can bias the internal transistors and cause a current consumption of up to uA.
To avoid this situation, configure any unused pin as a digital output and drive it to either low or high. As you can imagine, choosing datasueet correct type of power supply to have a central role in optimizing the energy efficiency of the device. Apart from the cons and pros of each ddatasheet, other parameters such as how much current the supply needs to operate and its efficiency need to be carefully analysed to chose the most datasheef solution.
It is well known that switching power supplies are much more efficient than linear darasheet.
This is because losses in SMPS are mainly a factor of the internal resistance and switching frequency of the MOSFET used plus the voltage drop at the diode, while in linear regulators most losses come from the voltage drop at the regulator transistor.
SMPS is an ideal choice when the difference between Vin and Vout is more than a couple of volts and a high current constant load needs to be powered, as they provide much greater efficiency as shown in the calculations. But when a device spends most of its life in sleep mode, consuming below 1mA of current, a linear voltage regulator should be considered.
Therefore, for embedded systems with long sleep times, a linear voltage regulator should be considered as a viable a choice. Efficiency is understood as the ratio of the power lost in the conversion process given by the equation:. The efficiency is determined by the power losses as seen above plus the power required for the component to work.
Another parameter to watch out for is the required current for the voltage regulator to do the voltage conversion, 78805a also known as quiescent current. Silicone manufacturing technology and design techniques improve every year.
This allows IC manufacturers to datashest better components in many aspects, such as improving their efficiency. Here is a comparison between two step up converters efficiencies, the LM released on and the TPS released on Pricewise, the LM costs around 2. Linear regulators need to drop a minimum amount of voltage at their input in order to supply a certain amount of current.
Here is a comparison of the required voltage drop between the classic A very old and the TPS released in As you can see from the above graphs, the A needs to drop at 7805s 2V in order to source 1A of current at 25C while the TPS only needs to drop 40mV to source the same current at the same temperature.
This is a massive improvement.
The datasheer of the A is 0. As in efficiency improvement, there is also a massive difference in price. Only interested in applying these guidelines to your design? Download the Power Optimization Guide. Your email address will not be shared and you will only receive relevant content. This section dives into low-power design techniques for Integrated Circuits and passive components.
This is normally advertised on the first page of the datasheet. In AC mains powered systems, this solution is normally more than enough, however in battery-powered systems with very tight power budgets, sometimes you need to disconnect the device from the power rail in order to remove all current consumption.
(PDF) 7805A Datasheet download
Power wise, the difference is negligible, so the choice comes down to the following design parameters:. Bipolar Junction Transistors require a base current which needs to go through the MCU if the transistor is connected to one of the digital outputs. While for a BJT driving the same current and a voltage drop between collector and emitter of a typical of 50mV we have a dissipation of:. R2 is not essential, however, it is good practice to place a pull-down resistor in order to guarantee a low level in case that the IN pin is floating or high impedance.
After fully charging a capacitor, a tiny amount of current will still be flowing between the positive daatasheet negative plates. Leakage current is a function of the dielectric used, the voltage applied to the capacitor and the capacitance.
In this case, leakage is not really a problem in terms of power consumption. However, in a battery system that requires big electrolytic capacitors for decoupling or bypassing, leakage can become an issue. As a general rule of thumb, avoid the use of high capacitance dtasheet capacitors in battery powered systems. Resistors hanging from the power supply line with a path to GND are a constant source of current consumption on the circuit.
As a general rule, when a pull-up resistor is needed by any circuit, you should try to use the highest value possible, which is typically 47K or 51K ohms.
This works great for signals that are not linked to a communication bus. The resistors sizing guideline also applies to voltage dividers. Instead of using a 1. Your circuit will be less immune to noise, but depending on the application, this could be acceptable.
PDF 7805A Datasheet ( Hoja de datos )
Where possible, on power traces that will handle a considerable amount of current, make the PCB copper traces as wide as possible. This technique will reduce the resistance of the track, therefore less heated will be dissipated. At the beginning of the article, it was mentioned that some of the optimizations explained have a very datasheft impact on the power consumption of the device, dataxheet other will just improve it a small amount.
Software optimization is probably the most relevant tweak you can do to your device in order to reduce its power consumption. Interruptions are events triggered by either an external signal or an internal peripheral of the MCU such as a timer or ADC conversion flag.
An interrupt based software operates on the premise that it only needs to execute code when certain inputs or conditions are present, the rest of the time the circuit goes to sleep. Not all waiting times are the same.
Selling A, AF, CT with A, AF, CT Datasheet PDF of these parts.
Sometimes you are waiting for an ADC conversion to finish datasheeg could take us, other times waiting for a button to be pressed which could take hours and in some situations, only a single datashwet of the MCU such as a PWM needs to be used. Because of this situation, MCU manufacturers have created dattasheet low power modes. Considering our previous situations we could say that each of them could be paired with a low power mode:. Implementing an interrupt datazheet code with low power modes, can drastically improve the power consumption of a device and make datashwet better product altogether.
Each code is different and unique, however, some effort should be put into creating ways to avoid repetitive CPU intensive tasks. For example, in the Solar Mobile Charger, a subroutine will calculate the input power of the device by multiplying 7805x sensed input voltage with the sensed input current.
This multiplication will use floating point arithmetic, therefore it will be a CPU intensive operation. There will be times when the input voltage and current will remain the same such as during a sunny day and while the voltage of the battery is below its nominal level. Depending on the device, this strategy could make more or less sense, but it could drastically lower the power consumption on a system where the parameters vary very little.
This is an industrial device that needs to monitor and store the voltage value of 2 LiOn batteries connected in series. The device is far away from the batteries, therefore a big capacitor is used to keep the voltage stable and handle datasbeet peaks.
The CAT24M01 is selected. This memory communicates using I2C. The typical power consumption is 4mA when data is being written on the memory and 2uA when no operating. This device will not go into sleep mode.
After performing a conversion, sending and storing the data, it will enter a while loop until a timer of 1 second has expired and then repeat.