EDGE™ prepared by Prof. George Slack (EE) Copyright © 2006 Rochester Institute of Technology All rights reserved. Noise Immunity Transients and ESD Practical Design Considerations

EDGE™ noise immunity Circuit noise immunity is the ability of a device or component to operate in the presence of disturbances. Caused by: 1.Electro Static Discharge - a sudden power discharge. A rapid high voltage, high current transient. 2.Noise disturbance - a frequency spectrum above or below the intended frequency response of the designed device but usually within the expected voltage range.

EDGE™ Types of noise Types of noise EMI - Power surgesEMI - Power surges (ElectroMagnetic Interference) An electrical disturbance in a system due to natural phenomena, low-frequency waves from electromechanical devices or high-frequency waves (RFI) from chips and other electronic devices. Allowable limits are governed by the FCC.  RFI – high impedance devices requiring very limited current. (Radio Frequency Interference) High-frequency electromagnetic waves that emanate from electronic devices such as chips. If the source is sufficiently strong this can enter your circuit.

EDGE™ When is Noise Immunity design needed? Senior Design I – –Paper Design wks 1-8 Senior Design II – –Prototype device testing wks – –Pre-integration testing with lab equipment DUT (device under test). Wks 3- 6

EDGE™ Where does noise get into electronics? through power supply connectionsthrough power supply connections through ground connections and loopsthrough ground connections and loops through signal inputsthrough signal inputs through human touch- ESDthrough human touch- ESD through debug or hardware simulationthrough debug or hardware simulation

EDGE™ CMOS gates & Transients High Impedance CMOS gate will not allow transients to be absorbed. CMOS inputs have very high input impedance. This is good for low power consumption for well protected electronics but susceptible to misuse when connecting to the outside world. Misuse during debug and testing.Misuse during debug and testing. ESD and reverse polarityESD and reverse polarity –Solution: Diode circuits to protect against reduce transientsreduce transients – Solution: Low pass filter

EDGE™ Protection Practices Electronic Solutions: Bridge to block reverse polarity,Bridge to block reverse polarity, Schottky diode: very fast switching times and low forward voltage drop. As low as 0.15 volts for low ma applications.Schottky diode: very fast switching times and low forward voltage drop. As low as 0.15 volts for low ma applications. Zener diode across the input.Zener diode across the input. AC Circuit breaker – GFIAC Circuit breaker – GFI

EDGE™ Polarity Protection + Input Port – (+) (–)(–) + Input Port – 1N5822 or 1N5817 1N4001 Schottky diode

EDGE™ Over-voltage Protection Fuse 1N5339 (5.6V for a 5.0V input) + input port – (+) (–)(–) Zener diode

EDGE™ Over-voltage Protection for Digital Inputs

EDGE™ Lowpass Filter

EDGE™ 1. 1.CRITICAL: When considering various input and output devices, acquire manufacture’s specification sheets. (Also, many spec sheets show application circuits which may speed up your design.) 2. 2.Noise versus signal response needs (i.e. CMOS versus TTL ) Control Voltage (Vdd vary from 1.5 VDC to 12 VDC typically) 4. 4.Needed minimum Signal Transient Response RLC loads (dangerous current and voltage spikes) 6. 6.Apply to Thevenin Equivalent Circuits – –Source electronics – –Device being driven Knowing Your Design Specifications

EDGE™ Isolating Noise Digital and Analog Optocoupler /OptoisolatorsDigital and Analog Optocoupler /Optoisolators –an electronic device that uses optics to transfer a signal while keeping the receiving and transmitting circuits electrically isolated Digital Isolators – Power IslationDigital Isolators – Power Islation Somewhat expensive ($1/ channel) but good isolation.Somewhat expensive ($1/ channel) but good isolation. (Analog Devices) (Analog Devices) nsec repsonse, > 30 VDC outputs,nsec repsonse, > 30 VDC outputs, Power connections - Design for Transit current spikes.Power connections - Design for Transit current spikes. Shielding at high frequency response needsShielding at high frequency response needs Fiber Optics at giga hz response needsFiber Optics at giga hz response needs What does not work? –Fuses are typically ineffective since a fuse is too slow to stop ESD and transient current spikes usually due to inductive loads but good for harness short-circuit or misuse.

EDGE™ Isolators Analog Devices, Isolators 55F,00.htmlAnalog Devices, Isolators 55F,00.html 55F,00.html 55F,00.html Isolators: /0,2877,ADuM2401,00.htmlIsolators: /0,2877,ADuM2401,00.html /0,2877,ADuM2401,00.html /0,2877,ADuM2401,00.html Attached pdf’s of Spec SheetsAttached pdf’s of Spec Sheets

EDGE™ Articles, recommendations, components and spec sheets short circuit protection circuits; Manufacture’s short circuit IC. EMI/ RRI Filters EMI RFI EDN Article Conductors %20circuit%20protection%22 Design Standards UL 489 and UL1077 standards