1. Purpose This course discusses techniques for analyzing and eliminating noise in microcontroller (MCU) and microprocessor (MPU) based embedded systems. Objectives Learn about how packaging affects efforts to reduce EMI. Understand the necessity for carefully designed decoupling capacitors, such as three-pin teed-through types. Find out how to evaluate EMI countermeasures. Discover the best way to implement EMI reduction techniques. Content 15 pages Learning Time 30 minutes Course Introduction

2. Reducing EMI EMI reduction is a goal shared by both the semiconductor experts who design MPUs and other LSI devices and by the engineers who apply those chips in embedded systems ECU Electronic Control Unit EMI Electromagnetic Interference Explanation of Terms A microcontroller chip is composed of a core, I/O ports, and power supply circuitry. The core consists of the CPU, ROM, RAM, and blocks implementing timers, communication, and analog functions. Power supply Two power supplies are applied to the LSI: Vcc and Vss. The core power supply internal to the LSI is VCL (internal step-down). The Vss-based power supply routed through the LSI is VSL. Harness Cables (wires) connecting a board and power supply or connecting one unit in a system to another Balun LISN TEM Cell WBFC Core A room designed to block radiation from the outside and to minimize reflections off the room’s walls, ceiling, and floor A passive electronic device that converts between balanced and unbalanced electrical signals CISPR 25 International Special Committee on Radio Interference (CISPR) publication 25: “Limits and methods of measuring radio disturbance characteristics for the protection of receivers on board vehicles.” CISPR is a sub-committee of the International Electrotechnical Commission (IEC). Line Impedance Stabilization Network Transverse Electromagnetic Cell Workbench Faraday Cage Anechoic chamber Page 2 Delete the thin line through the illustration

3. Design goal for EMI reduction: Increase current supply from decoupling capacitor (Cdc, loop B) and decrease current from main power supply (loop A) as much as possible - Current ratio A/B is determined by the impedance ratio: If possible, this ratio should be <1/100 (-40dB) Two methods for reducing EMI: Increase loop-A impedance by inserting ferrite bead in loop Decrease impedance of loop by decreasing its inductance - Make the loop area as small as possible to minimize its inductance - Use feed-through capacitors because they have intrinsic impedances less than 1/10th those of conventional SMD ceramic capacitors Supply Decoupling Basics Loop B Loop A

4. 1313: 240 pins1111: 256 pins2727: 256 pins2828: 208pins QFP BGA Typical Die size WLP FBGA (Fine-pitch BGA) CSP 28 mm (256 pins/0.4 mm) BGAs and CSPs Save Board Space Smaller chip packages allow products to become more compact and convenient, but complicate design efforts to place decoupling capacitors where they will be most effective for reducing EMI

5. 27mm BGA Decoupling Capacitors for BGAs Top of circuit board for mounting a BGABottom side showing placement of bypass caps Finding sufficient mounting space can be a problem!

6. V CPU Low-ESL Bypass Capacitors Multi-pin IDC-type capacitor achieves low supply impedance Three-pin SMD feed-through capacitors provide very good connections - No extra paths, so 100% of supply current is fed through 3-pin feed-through capacitor* Design alternative: IDC-type capacitor achieves low supply impedance *Source: Murata Manufacturing Page 6 Problems with Narration

7. Current measurement points (Vcc, PVcc, Vss) Pads for inductors (ferrite beads) Typical decoupling capacitor Evaluation of Supply Decoupling Area under device showing pads for decoupling capacitors Power supply connections Top of evaluation boardBottom of evaluation board Page 7 Slide Changed (Text moved to left, away from top photo.)

8. Evaluation Example * MPU: SH7055R Frequency: 80MHz Near-field tests* using the evaluation board allow comparisons of levels of RF current in the power supply lines 12 bypass capacitors addedFerrite bead + 12 capsNo filter components

9. Near-field Tests MPU: SH7055R (40MHz) Capacitor Tests with 256-pin QFP Twelve 3-pin capacitors (0.1µF each) VDE measurement point NFM21 Caps (for Vcc) Caps (for PVcc, AVcc) 256-pin QFP Macro (sensitive) probe @80MHz -20dB One 3-pin capacitor (NFM21: 1µF)

10. All Decoupling caps : on bottom side NFM21 Caps (for Vcc) Caps (for PVcc, AVcc) Capacitor Tests with 256-pin BGA 256-pin BGA MPU: SH7055R (40MHz) Macro (sensitive) probe @80MHz Near-field Tests Eight 2-pin capacitors (0.1µF each) -20dB One 3-pin capacitor (NFM21: 1µF)

11. Near-field tests reveal EMI problem distant from MPU - Magnitude of noise near output connector of ECU-B is 20dB higher than that of ECU-A MPU Scan for EMI at All Locations ECU-A: Good EMI performanceECU-B: Excess Leakage ECU package Page 11 Problem with slide — Dotted lines in scans have been replaced with solid lines and moved. Please correct.

12. Data Shows Progress — and Problem Noise reduction efforts were successful for both ECUs, yet insufficient for ECU-B - Target level was exceeded by ECU-B’s design x Without caps With caps With caps+FB ECU-A ECU-B 60 40 20 Noise Current (dBµV) 0 Target Level Test data showing decoupling effects on basic boards Test data showing degradation on ECU-B Frequency (MHz) パスコン + インダクタ - Test data when decoupling capacitors and ferrite bead were used Noise Current (dBµV) - Test data when decoupling capacitors were used Noise Current (dBµV) Page 12 Problem with slide — Text in the two data traces is missing, and “Frequency (MHz) “ is obscured.

13. Effects of Adding Components Using a ferrite bead and multiple decoupling capacitors is an effective way to reduce EMI Vcc GND Capacitor I/O current Core current Ferrite bead Decoupling capacitors Power plane Ground plane (no slit) Slit (moat) Page 13 Problem with slide — Block diagram (bottom right) is broken up and moved down.

14. Countermeasure Implementation It’s best to follow a step-by-step EMI reduction procedure: Find the most important noise contributor and eliminate/reduce that problem; then repeat the process until design goal is met Reducing noise from unimportant element has no effect Reducing noise from important element drops overall level by 3dB 60 50 40 30 -10dB EMI level (dB) Effect: -3dB Before counter- measure After counter- measure Noise element B Resulting noise level Noise element A 60 50 40 30 -10dB EMI level (dB) Effect: 0dB Before counter- measure After counter- measure Noise element 2 Noise element 1 Resulting noise level Page 14 Problem with slide — Vertical arrows should be dotted, not solid.

15. How packaging affects EMI reduction Three-pin SMD feed-through capacitors Evaluating EMI countermeasures Iterative method for countermeasure implementation Course Summary For more information on specific devices and related support products and material, please visit our Web site: http://america.renesas.com Page 15 Problem with slide — Text in the yellow block should be contained within the box, as shown here.