EMC Lab presentation

Objectives of the Lab Objectives Understand basic set-up and methodology for characterization of emission of ICs according to IEC 61967 (1 ohm and TEM cell method and near-field scan) Understand basic set-up and methodology for characterization of emission of ICs according to IEC 61967 (DPI and TEM cell method) Characterizing the emission and the susceptibility of a commercial circuit Test the influence of some circuit’s parameters on emission or immunity Correlate S/Z parameters with susceptibility to RF disturbance

Planning of the Lab Day 1: emission measurement Configuration of a spectrum analyzer for emission measurement Measurement of conducted emission due to the switching of an I/O. Measurement in time and frequency domain Effect of I/O options on electromagnetic emission Use a near-field scan probe to locate current circulation and evaluate current characteristics Use near-field scan probe to measure the influence of spread-spectrum frequency modulation on electromagnetic emission

Planning of the Lab Day 1: emission measurement Case study presentation: Slew Drive Vddrio = 3.3 V Vdd_core_io = 1.2 V Vddrio Vdd_core_io Vdd_core_io Vddrio Dig_Out Dig_In Vss_core_io Vssrio Vss_core_io Vssrio Vssrio Vss_core_io 49 Ω Drive Slew Reduced High 1 Full 1 Ω

Planning of the Lab Day 1: emission measurement 1 Ω measurement of I/O noise in time domain Observe simultaneously the buffer output voltage and the voltage captured by the 1 Ω probe Compare the voltage profiles with the different I/O options

Planning of the Lab Day 1: emission measurement 1 Ω / 150 Ω measurements of I/O noise in frequency domain Compare the noise in the four I/O options 1 Ω measurement

Planning of the Lab Day 1: emission measurement Near field scan – evaluate current circulation

Microstrip line (w = 1 mm, h = 1.6 mm, L = 10 cm) Planning of the Lab Day 1: emission measurement Near field scan – evaluate current circulation Link between two CMOS inverters: Magnetic-field probe Inverter AHCT04 Inverter AHCT04 Microstrip line (w = 1 mm, h = 1.6 mm, L = 10 cm) 10 MHz With magnetic near-field probe, locate the circulation of the current What is the bandwidth of the current ?

Planning of the Lab Day 1: emission measurement Near field scan – microcontroller and effect of spread-spectrum frequency modulation on emission The microcontroller Freescale MPC5604B has the following configuration: CPU running at 40 MHz Internal clock produced by an on-chip PLL running at 80 MHz, synchronized by a 8 MHz quartz oscillator 13 I/O switching at 200 kHz With a near-field probe, locate the main source of electromagnetic emission created by the microcontroller. Test the influence of spread spectrum frequency modulation on PLL emission

Planning of the Lab Day 1: emission measurement Near field scan – microcontroller and effect of spread-spectrum frequency modulation on emission VDDHV/VSSHV (I/O supply) 5 I/O switching at 200 kHz VDDHV_ADC/VSSHV_ADC (ADC supply) VDDLV/VSSLV (Core + PLL supply) 8 I/O switching at 200 kHz External quartz

Planning of the Lab Day 2: susceptibility measurement Presentation of the DPI test bench. Injection on simple loads and computation of power Analysis of bias tee and identification of operating frequency range. Measurement of conducted susceptibility of LTC1798. Manual and automatic DPI tests. Influence of the input filtering. Analysis of the susceptibility curve. Comparison with S parameter profile. Measurement of radiated susceptibility in TEM cell of LTC1798.

Planning of the Lab Day 2: susceptibility measurement Bias tee C = 1 nH, L = 1 µH S parameter characterization:

Planning of the Lab Day 2: susceptibility measurement Case study presentation: LTC1798-2.5 from Linear Technology Bandgap references Input voltage = 2.7 V to 12.6 V Output voltage = 2.5 V +/- 10 mV (0 – 70°c) Output current = up to 10 mA

Planning of the Lab Optionally mounted Day 2: susceptibility measurement Test board: 4-layer board, TEM cell compatible Connection to the disturbance to P1 SMA connector (input of the reference) Optionally mounted

Planning of the Lab Day 2: susceptibility measurement Observed failures : DC offset induced at the reference output Injection on input, no filter, Femi = 300 MHz Injection on input, no filter, Femi = 10 MHz

Planning of the Lab Day 2: susceptibility measurement DPI injection on input pin - susceptibility threshold

Planning of the Lab Day 2: susceptibility measurement DPI injection on output pin - susceptibility threshold

Port 1 = input, Port 2 = output Planning of the Lab Day 2: susceptibility measurement Link with S parameter measurements of test board and bias tee Port 1 = input, Port 2 = output

Planning of the Lab Day 2: susceptibility measurement Radiated susceptibility test in TEM cell Find the frequencies where the circuit is susceptible Find the worst case orientation of the test board