1/18 Near field scan immunity measurement with RF continuous wave A. Boyer, S. Bendhia, E. Sicard LESIA, INSA de Toulouse, 135 avenue de Rangueil, TOULOUSE cedex, France.

2/18 1.Introduction : immunity methods overview 2.Description of the near filed scan immunity method 3.Modeling of the aggression 4.Case studies 5.Conclusion Outline

3/18 Introduction : immunity methods overview MethodsAdvantagesDrawbacks DPI IEC (localized method) Simple model Low power, Low cost Frequency limit 1 GHz BCI IEC (localized method on N pins) Cable injection No specific test board Test on actual production boards Frequency limit : 400 MHz Weak coupling TEM/GTEM IEC (Global aggression) High frequency method Weak coupling Complex coupling Special board Mode Stirred Chamber IEC (Global aggression) High frequency method Far field Complex model Much space and expensive Objective : Find a simple method to characterize and investigate the immunity of each part of a circuit at high frequency

4/18 Near field probe RF generator Field produced by the probe Lead frame device under test Parasitic induced currents Principle Test bench Description of the near field scan immunity method Reuse of near field scan in emission (IEC ) Injection of RF disturbances by a miniature near field probe Advantages : Few mm Magnetic probe  Localized disturbances coupled on lead frame of packages  Produce immunity cartography or scan  No specific test board or test fixture required  Frequency limitation : several GHz, linked with the resonances of the antenna

5/18 Description of the near field scan immunity method General set-up of near field aggression experiment Generation of continuous wave aggression. The use of a directional coupler allows to know the forward power in the injection loop. Results are given in terms of forward power. For each frequency, the forward power is increased until the failure is detected The forward power that creates a failure is stored. The probe is then moved to a new position Signal synthesizer Amplifier Nearfield probe Device under test Oscilloscope Failuredetection: Pattern exit Pforw Directional coupler Prefl

6/18 Modeling of the aggression Electrical modeling of the probe H i Tangential magnetic field probe Validation of the model up to 10 GHz No antenna resonance below 10 GHz n dS Ground plane I1I1 L 1 L 2 RF Generator Electrical modeling of the coupling Inductive coupling Interesting method to evaluate the mutual coupling coefficient : PEEC method L=0.13m, ε r=2.2 Line with losses Inductive load SPICE model for the magnetic probe

7/18 Modeling of the aggression Partial Element Equivalent Circuit to find mutual coupling Conductor A Conductor B Ia Ib Inductive coupling L ab 1.All conductors are meshed in elementary filaments 2.Inductive coupling between conductors is computed by adding the influence of all filaments on each other : 3.Gives directly an electrical model which can be simulated under SPICE. LaLa LbLb L ab

8/18 Coupling vs. position Good correlation for maximum coupling Coupled power vs. probe position Electrical modeling of the coupling: Validation Validation case : coupling to a micro-strip line Modeling of the aggression 50Ω ε r=2.2 xy z h=1mm 40dB Amplification Signal synthetizer P measured (dBmW) Spectrum analyzer Scan on X +20dB/dec. Transmission coef. vs. frequency Efficient coupling at high frequency Model valid until 6 GHz

9/18 Modeling of the radiated magnetic field r  b x y z r H   H   E  I r  b x y z r H   H   E  Elementary loop Modeling of the aggression Based on the approximation of the elementary loop crossed by a current Comparison with measurement – Calibration of the injection loop Calibration of the injection loop to determine the radiated field as a function of the incident power, the frequency and the distance. h=1mm RF Generator Spectrum analyzer Measurement probe (calibrated) Injection probe x y z Good correlation until 2GHz Hy(f) for h=1mm Hy(x) for h=1mm and f=500MHz

10/18 Development of a tool under IC-EMC : Compute coupling between a magnetic probe and the package leads Build a SPICE-compatible electrical model of the aggression Compute H field Modeling of the aggression IC-EMC Immunity simulation flow : Ibis file Package geometry DUT SPICE model SPICEnetlistof DUT+aggression Probe dimensions H field computation IC-EMC FoPo SPICE Immunity criteria checked ? no Extract forward power yes Transient simulation Results

11/18 Aggression of the PLL of a 16 bit microcontroller Case studies Hy Scanned area Tangential H field Frequency 490 MHz Scan height 0.25 mm Criteria : 5% variation of the frequency of the bus clock Immunity cartography Apparition of a weakness zone located on the digital supply of the PLL pin (VddPLL) VddPLL aggression vs. frequency Quartz susceptibility 450 MHz Impedance between VddPLL and Vss core Correlation between immunity threshold and impedance between VddPLL and ground of core Vss 450 MHz

12/18 Case studies Aggression of the PLL of a 16 bit microcontroller A measurement in a TEM cell has been tried : no failures detected.  H field generated close to the probe above a pin of a TQFP 144 package:  Theoretical H field generated in TEM cell : For an equivalent power, the maximum H field generated by the probe is 20 times greater than in TEM cell. H=1mm Pforw = 31dBm F=480MHz Hmax=9A/m Hmean=3.6A/m Htot (A/m)

13/18 Aggression of a 10 bit ADC of a 16 bit microcontroller Case studies Hy Scanned area VSSA AN0 Tangential H field Frequency 500 MHz Scan height 0.25 mm Criteria : LSB modification Highlights 2 susceptible areas located on the analog ground of the ADC pin (VSSA) and on the input of the ADC channel (AN0). AN0 aggression vs. frequency Aggression of the input of the ADC In-band aggression VSSA influence High frequency susceptibility  Weakness at low frequency (in-band aggression) which depends on conversion clock  Weakness at high frequency (800MHz-1.4GHz)  Second weakness linked with VSSA susceptibility (see next slide)

14/18 Case studies Aggression of a 10 bit ADC of a 16 bit microcontroller VSSA aggression vs. frequency Aggression of the analog ground of the ADC Correlation between immunity threshold and impedance between VSSA and supply rails of core Vdd/Vss. These weaknesses are linked with supply impedance resonances Impedance between VSSA and Vdd/Vss core In-band aggression  Weakness at low frequency (in-band aggression)  Weakness around 500MHz 500 MHz 450 MHz

15/18 Case studies Aggression of an input port of a 16 bit microcontroller Near field aggression of an input portDPI aggression of an input port Two different injection methods, two different results. Only one common point : susceptibility level decreases with frequency above 1 GHz. Does the same model predicts these 2 results ? Currently, only DPI injection modeling has been established. Near field injection is on going.

16/18 Case studies Aggression of an input port of a 16 bit microcontroller Susceptibility SPICE model Model of DPI injection valid up to 1.8 GHz Z model shows the influence of the different parameters Injection path model measure Block behavior model Measure/given IBIS model Measure/given Passive Distribution Network Measure/ICEM Reuse of the ICEM model built for emission. Useful blocks to build a susceptibility model in DPI :

17/18 Case studies Aggression of an input port of a 16 bit microcontroller Comparison DPI injection measurement/simulation Comparison measure/simulation of forward power Comparison measure/simulation of transmitted power Good correlation until 900 MHz. Model built from first order parameters, without any confidential data High influence of the injection path and of the PDN and IO model. Essential parameters for a future ICIM model. Simulation problem

18/18 Conclusion A method of susceptibility characterization of ICs using near field has been presented. Main advantages :  Valid until 6 GHz  Help to detect susceptible pins of the integrated circuits  Simple inductive model A modeling software have been developed to predict the coupling, the radiated field and build an electrical model for susceptibility. Several cases have been presented which shows different effects of near field aggression. Future work : propose this method as an extension of BCI standard method to higher frequencies