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Circuit design considerations for embedded systems

Developing the circuitry of the embedded systems goes through different steps and the designer should acknowledge these requirements before initiate the design process.

circuit board

Embedded systems are designed to operate for specific purposes only and are optimized to fulfill different parameters like power, performance, cost, and timing. Designing the embedded systems is full of challenges as the design process of the embedded design includes various optimization activities with the requirement of different specifications for different conditions.

The circuit design of consumer electronics devices like mobile phones, laptops, and more devices need to be built in a way that they can withstand knocks, drops, or get submerged in water without losing its operational ability.

Developing the circuitry of the embedded systems goes through different steps and the designer should acknowledge these requirements before initiate the design process. Ignoring any one step can lead to the wrong development of the embedded system, which can lead to failure of the device that can cost hefty expenses after the final design phase. TronicsZone, a company specializing in this area recommends the following practices to ensure success & reduce risks.

Before starting to work on the circuit design of the embedded systems, it is important to know these two parameters:

  1. Acknowledge at hand power budget: Understanding the complete power budget for designing the embedded system will help you select the right components/chips and other necessary factors.
  2. Measuring the overall power consumption: The overall power consumption of the circuitry can be deduced with the help of a block diagram when designing the embedded system. The use of a block diagram will aid the designer to recognize the major components of the circuit and their power consumption limits. Make dedicated application notes and datasheets to get this information about the devices.

The above-mentioned factors will help the embedded system circuit designer to build a high-level embedded circuit design to achieve less power consumption and high performance plus efficiency. It will also help the engineer to understand the right requirements of the chips/components and other important parameters in the early design phase of the embedded system. To design an effective embedded system, the following is the list of some useful circuit design considerations which can be used by the designer for designing the embedded system boards.

Keeping a check on the overall circuit operating voltage

It is important to maintain a low operating voltage for the overall circuit board because power consumption is related to the operating voltage. The higher the voltage level of the circuit, the higher the power consumption, so it is advised to keep the voltage level as low as possible. E.g. if every chip in the circuit can draw the voltage level up to 2.7V, then the designer can consider setting a small margin to the particular voltage level for the complete circuit design board.

On the other hand, if there is a suitable power saving option on the circuitry, then the designer can easily fulfill the requirement of more than one power-rail, which is needed by the embedded system board, however, some additional equipment like digital translation chips and DC-DC converter will be needed to complete the board design.

Maintaining the operating voltage of energy-hungry devices

The operation of energy-hungry electronic devices should be regulated at low voltage as it will help to minimize power consumption. To accomplish this step, some additional devices like LDO/ DC-DC converter and external voltage translator will be required to make interfacing with different equipment/components in the circuitry which are working at disparate voltage levels. Before going for this procedure, make sure to check the additional cost, effort, power-saving, and wake up time will be required in the circuit design.

Choosing the right chips and components

The selection of the right components and IC chips is highly important when drafting a schematic of the embedded system as it affects the efficiency and performance of the device. It is also necessary to consider the complete power consumption budget as the power consumption will have a greater impact on the circuit. So, the designer must choose ICs with high/low power consumption depending on the circuit design, whether it will operate at a high/low voltage level. One should also acknowledge other important factors when choosing the components and chips for the circuitry.

Use of various interfacing modules

The circuit design of the embedded system may require the need for using other ready-made devices like sensors, cameras, IoT modules (Bluetooth, WiFi, etc.), RS485/ RS232 communication interfaces, etc. It is important to consider the power consumption of these interfacing devices before selecting them. To choose the right type of technology can be ideally measured by comparing several parameters like active power consumption, power-up time, the ideal power consumption of different devices.

E.g., if the designer wishes to use RF for transferring data, then he/she needs to consider the suitable device from WiFi, BLE, ISM RF, Zigbee, etc which will provide a great user experience and consume less power. Most of the time the selection of incorrect technology leads to difficulty in optimizing power consumption in the circuit design. Hence, it is important to give considerations to these factors as well.

Peripheral power gating

In electronic circuit design, the mechanism of controlling power can be integrated to make the device OFF when it is not being used. Certain embedded systems use communication modems and keeping them ON for the whole time could impact the expense from the view of power consumption. So, it is better to use the ON/OFF power control to put the power down on the device when it is not in use. Other components like sensors, ADC, LCD, etc. should be switched off when they are also not in use as it will help to reduce the higher consumption of power in the circuitry.

Use of right power supply

It is highly essential to choose the accurate input voltage which will operate on the embedded board. Either the input voltage is delivered by the power supply adaptor or battery; it needs to be correctly measured. If every component on the circuit board is operated at 3.3V or 5V, then it is better to use 6V power input rather than making use of 12/24V battery or DC input as it will help to prevent the power loss in the circuitry as power loss is directly related to the voltage difference.

For voltage conversion of the embedded board, the designer should make use of switching DC-DC converter rather than a linear regulator. Linear regulators operate highly ineffective in voltage conversion as these devices on the dissipation mode in which power is equivalent to the difference in the voltage and current dissipated in the form of heat.

LEDs placement

The placement of LEDs on the embedded board can largely impact the power consumption of the circuit design. A single LED can consume up to 1-5mA in the circuit. So, if there is a need for using LEDs on board, then the designer should try reducing the LEDs. It will be better if the LEDs are completely removed if possible.

Otherwise, the designer must try to minimize the brightness of the LEDs with the help of high valued resistance. Either the engineer can set the LEDs to blink only rather than making them glow for full time or keeping it OFF until the user requires communicating with the device. Such approaches will help to reduce the power consumption in the overall circuit.

Selection of right display

When selecting the display for the embedded board, an engineer has several options to go for such as Paper Display, 7 Segment display, OLED, Mono Graphic LCD, Character LCD, Glass LCD, etc. Since the display consumes over 50% to 60% of the overall power consumption, so the designer must choose the display carefully, keeping in mind the overall power consumption budget delivered by the whole circuitry.

If it is certainly compulsory to use the display with a high power consumption rate, then the designer should implement other techniques such as full display, backlight power gating, display size, color scheme choice, such as grey or dark scale mode, which can aid in minimizing the power consumption drastically.

Use of pull-up resistors

Using the pull-up resistors of optimal values can aid in reducing the power consumption in the circuitry. Pull-up resistors are majorly used for keys, I2C, etc. Every pull-up resistor can help to save up to a few milliamperes. So, the use of pull-ups can significantly help in power saving. E.g. the pull-up resistor of value 1K will drain up to 3.3mA than the pull-up of value 10K, which will drain 330uA when operating at 3.3V.

Use of microcontroller (MCU)

The selection of the right microcontroller is important for the circuit design of the embedded systems. Depending upon the type of circuitry, the selection of high/low power consuming microcontroller can vary. Selecting the low power consuming microcontroller is critical if the power consumption of the MCU is 20% greater than the power consumption of the embedded system board.

So, making more effort in choosing the lowest power consuming MCU will not give much impact on the circuitry. It is important to pay heed to other factors that can help in low power consumption like power gating of the peripherals, setting the input level of floating point pins to a definite high or low state, optimizing code flow strategies, etc.

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