Strength Through Design
In an effort to meet the needs of embedded designers, silicon manufacturers continue to increase functionality and performance while decreasing the physical size and cost. This provides a significant benefit to both the embedded designer and end consumer, but as the demand for sophisticated consumer and embedded products continues to expand, so does the challenge of properly designing such applications. Not only must the embedded designer contend with meeting the product specifications, but as electronics continue to evolve into “smaller, faster and cheaper”, so does the inherent susceptibility to unwanted interference from outside electrical sources, otherwise known as EMI (Electromagnetic Interference). EMI can wreak havoc on an embedded application with results ranging from simple nuisances in a product’s operation to catastrophic failures causing a cease in product functionality. Whether integrating electronic intelligence into products such as an electric toothbrush or meeting the high standards required of medical equipment, creating the most electrically robust designs continues to be a necessary, but sometimes challenging endeavor. As an embedded system designer, priority must be given to not only meeting the product specifications but to also creating the most reliable end product by limiting the negative influence of EMI.
What is EMI/EMC?
EMI (Electromagnetic Interference) occurs when the electromagnetic field of one device has an adverse affect on the operation of another device. EMC or Electromagnetic Compatibility is the ability of an electrical system or device to operate properly in an electromagnetic environment without being affected by EMI, or affecting other devices with EMI within its environment.
EMC within electronic components has become an increasingly important issue for embedded designers to contend with. As system frequencies and the need for lower supply voltages increase, the end application becomes more and more vulnerable to the negative affects of EMI. These electrical influences can be generated by either radiated or conductive EMI sources. Radiated sources include anything electrical or electromechanical, including motors, power lines, antennas, traces on a PCB (Printed Circuit Board), and even the silicon components on the PCB. Conductive EMI primarily shows itself as electrical “noise” on the power supply lines of an application and can be caused by induced voltage spikes from other devices within a system.
One additional element of conductive EMI is EFT (Electrical Fast Transient). This occurs on AC power lines and can enter a system through capacitive coupling or supply injection. Applications most typically prone to EFT are capacitive or transformerless power supplies. Either EMI source can cause unpredictable operation of an application and result in electrical “latch-up” of the system. In the most severe instances, this can even cause complete failure of the device through EOS (Electrical Over Stress).
Ultimately, prevention of EMI within a particular application remains the responsibility of the embedded designer. This begins with the implementation of good board design practices including proper PCB layout and grounding, limiting trace lengths, placement of electrical components, as well as selection of the most EMI resilient silicon products.
Microchip’ EMI Defense
A direct result of Microchip’s commitment to continuous improvement, Microchip’s EMI protection is a compilation of years of EMI/EMC engineering experience and direct feedback from embedded designers. Microchip has implemented a multifaceted approach to creating PIC microcontrollers that are less sensitive to EMI and limit EMI emissions within an electrical environment. Defense against EMI also incorporates methods to deal with EFT, as well as bursts of ESD (Electrostatic Discharge).
Microchip realizes the challenges of the embedded engineer, and has developed technology to decrease the susceptibility to EMI/EMC and provide the most electrically robust products available in the industry.
EMC Advantages of Microchip Products
- Ease in EMI/EMC qualification and testing to the latest regulatory laws
- Reduction in radiated EMI emissions
- Enhanced electrical barrier of protection from ESD and EFT
- Lower system cost by reducing PCB filtering and isolation
- Electrically robust solution for long life reliability
- Higher immunity to injected noise and harsh electrical environments
- EMI/EMC equivalence with legacy Microchip Products
Microchip performs extensive EMI/EMC testing to validate the electromagnetic resilience of PIC microcontrollers, dsPIC® digital signal controllers, analog and memory products. EMI/EMC characterization is comprised of a full suite of tests that determine the emissions and susceptibility to both radiated and conductive EMI environments as well as variations due to ESD and EFT.
The engineers at Microchip understand the numerous challenges facing the modern embedded design engineer – schedules, meeting product definition, limiting project costs and creating the most electrically reliable products. Utilizing Microchip products in your application minimizes all of these design challenges by providing flexible solutions that are easy to design-in while providing world-class electrical stability. Any application can realize the benefits of Microchip’s electrically robust products, particularly those applications residing in electrically harsh environments such as appliances, automotive and industrial. Microchip’s contribution to limiting design challenges and the adverse affects of EMI within any application is demonstrated by real-world customer acceptance with a seemingly infinite number of applications powered by Microchip products.
Typical EMI Test Results - The data speaks for itself!
- Conductive EMI
- Radiated EMI
With so many methods of testing for EMI, Microchip implements selected industry standard testing methodologies considered to be among the toughest. The data shown demonstrates the conducted and radiated noise of a typical 8-bit
Flash Mid-Range PIC microcontroller.
Figure 1: Vdd Conducted Noise of a PIC Microcontroller with 8 MHz Internal Oscillator
Utilizing a spectrum analyzer, this test measures the noise that is directly coupled into the Vdd line from the PIC microcontroller. With a 5V power supply and 8 MHz internal oscillator, without the latest EMC silicon methodologies, the “BEFORE” PIC microcontroller generates a significant amount of noise throughout the frequency sweep. Though the amplitude of this noise is tolerable for most applications, implementing the latest EMC silicon methodologies, the “AFTER” PIC microcontroller only generates two data points greater than the “noise floor”. Demonstrating that the PIC microcontroller is actually operating, the spectrum analyzer captures the fundamental frequency of internal 8 MHz oscillator as well as the internal instruction clock running at one-fourth the internal oscillator. The change in resolution bandwidth is done as a means to efficiently acquire the data throughout the frequency sweep.
Figure 2: Radiated Noise of a PIC Microcontroller with 8 MHz Internal Oscillator
Utilizing a spectrum analyzer and a RF TEM-Cell, this test measures the noise that could potentially be injected into the surrounding electrical system from the PIC microcontroller. With a 5V power supply and 8 MHz internal oscillator, the “BEFORE” PIC microcontroller generates noise throughout the frequency sweep. This amplitude is tolerable for many applications, but implementing the latest EMC silicon methodologies the same PIC microcontroller “AFTER” does not generate any noise greater than the “noise floor” itself.
NOTE: The conductive/radiated noise data shown is a typical representation of 8-bit Flash Mid-Range PIC microcontrollers. Note that this will vary based upon process technology, product architecture, etc. Contact your local Microchip representative for specific Microchip product data.
Generally Speaking, EMC is defined as the ability of an electronic
system to function compatibly with other electronic systems.
A system is electromagnetically compatible if:
- It does not cause interference with other systems.
- It is not susceptible to emissions from other systems.
- It does not cause interference with itself.
Good EMC design practice helps avoid the needs for design rework after testing, so minimizing development cost and time-to-market.
The Goal of the EMC Design Center is to share techniques to improve EMC performance, based on real world example.
The most common terms are:
- EMC: Electromagnetic Compatibility
- EMF: Electromagnetic Field
- EMI: Electromagnetic Interference (capacitive or magnetically coupled noise)
- RFI: Radio Frequency Interference (RF energy reception or generation)
- EFT: Electrical Fast Transient (High Voltage or High Speed Noise)
Every PIC Microcontroller is capable of passing IEC61000-4-4 test at 4KV.