Practical Measurements considerations for GaN and SiC technologies ANDREA VINCI EMEA MARKET DEVELOPMENT MANAGER POWER ELECTRONICS

Practical Measurements considerations for GaN and SiC technologies ANDREA VINCI EMEA MARKET DEVELOPMENT MANAGER POWER ELECTRONICS

PLEASED TO MEET YOU 2

Evolving Test Solutions with Semiconductors WAFER PACKAGING MODULE PRODUCT EXPERIENCE ACROSS THE ENTIRE WBG TEST CHAIN 3

The measurement challenge WHY TESTING WBG BASED POWER DEVICES/CONVERTER IS COMPLICATED New technology adoption, new topologies adoption More sensitive Gate drive isolation, gate drive timing Switch high voltage/current very fast (high CMTI) Parasitic Simulations and measurements look different Packages and test boards probing no test points Lab equipment used so far seems no longer adequate 6 DECEMBER 2017 4

The measurement challenge WHAT WE SHOULD NEVER FORGET Accurate measurements rely on using suitable instruments Instruments influence the measurements (always) Connection of voltage probes can add parasitic inductance or capacitance to the circuit itself. Soldering just a short piece of wire does it too And today s discussion: The bandwidth of the measuring instrument is critical to see fast transients with high-frequency ringing.and Common-mode rejection spec is essential to verify if ringing we see is real or not! 6 DECEMBER 2017 5

GaN: how does it come in power converters? Inductance 6

Typical measurement configuration Voltage Characteristics Voltage Characteristics High side and low side Input, output, and supply voltages Absolute maximum and threshold Common mode transient immunity Current Characteristics Timing Rise and fall times Propagation delay Dead time Channel to channel delay GATE DRIVERS HALF BRIDGE CONF. Large dv/dt High side and low side V GS and V DS Absolute maximum and threshold Current Characteristics Timing Rise and fall times Propagation delay Dead time Channel to channel delay Double Pulse Testing 7

Is the oscilloscope still a good tool? YES IT IS, BETTER THAN EVER See 16x more digitizing levels on a 12-bit scope 8

What Measurement Equipment? PROBES HAVE BECOME THE PRIMARY LIMITING FACTOR How do I get the signal from the test point to the oscilloscope? V BUS Probe Types Single Ended Probes Traditional High Voltage Differential Probes Controller High Side Load Isolated Probes Current Probes Low Side Selecting the right probe for the job 9

Current measurements? HOW REQUIREMENTS CHANGE WHEN SWITCHING AT HIGH FREQUENCIES How do we measure switching currents? Hall effect current probe (HECP)? Rogowski coil (RC)? Current shunt (CS)? 10

Voltage Measurements? AT FIRST GLANCE, IT APPEARS EXISTING PROBES HAVE COVERAGE The probe with the highest differential voltage is 7 kv with ~ 5 ns rise time The highest performance differential probe at 1.5 kv has ~ 1.5 ns rise time Differential Voltage 10 kv 3.3 kv 700 V IGBT SiC High voltage differential probes coverage? Silicon GaN High dynamic range, sufficient performance High performance, sufficient dynamic range 100 ns 10 ns < 1 ns Rise Time 11

Bandwidth vs. Rise Time Considerations I AM GOING TO USE MY GOOD OLD PASSIVE PROBE Do not confuse your circuit switching frequency with potential aberrations frequencies you are searching for Hard Switching 12

Sub-nanosecond switching with low-voltage GaN HEMTs Measurement characteristics Switched voltage: 10 V Switching frequency: 30 MHz Measured voltage transition time: ~ 500 ps Does this probe have sufficient bandwidth? Maybe DC/DC Converter: 30V GaN half-bridge [1] [1] http://www.psemi.com/pdf/eval_kit/manual/pe29100evk.pdf 2x GaN HEMTs gatedriver Soft Switching Hard Switching Switch Node Voltage Slide content contributed by Stefan Moench, University of Stuttgart Measurement and Switching in Sub-Nanoseconds with 600 V GaN HEMTs 13

Keep Your Ground Leads Short THE TEST POINT ISSUE Trade-off of convenience versus performance Smaller loop area = Lower inductance, lower noise, cleaner meas. 14

Low Side Ground Considerations WHICH COMMON GROUND SHOULD YOU USE? Some high current designs have an additional source pin which is available as a ground reference Multiple low-side measurements: Not all parasitic inductances can be excluded from the measurements, even with 4-terminal transistor packages, which offer a source-sense SS terminal. A better measurement technique is to use a differential probe for the low-side [1] Solution 1: GND_PWR Gate-Source Measurement Switch Node Measurement Solution 2: GND_SS Gate-Source Measurement Switch Node Measurement [1] Infineon CoolMOS C7 Gold in TO-Leadless (G7) - a new SMD package using Kelvin source concept Slide content contributed by Stefan Moench, University of Stuttgart Measurement and Switching in Sub-Nanoseconds with 600 V GaN HEMTs 15

High Side Voltage Measurements HIGH SIDE GATE DRIVER Measurement Conditions The boost supply voltage is a relatively low voltage referenced to the switch node Gate driver output is also referenced to the switch node Measurement Challenge Example: Measure a small differential voltage (± 15 V) in the presence of a large common mode voltage (600 V) when the switch node transitions very quickly (20 ns) The driver s high side output or boost supply voltage and local GND are tied to the switch node and will float up and down with the switch node V DIFF V CM ± 15 V < 600V The switch node is rapidly switching between V Bus (600 V) and ground (0 V) Switch Node 16

High Side Measurement Challenge POOR COMMON MODE REJECTION VISIBLE EVEN IF NOT SPECIFIED IN DATASHEETS This measurement is swamped out by the common mode error 615 V 15 V 600 V 17

How is Common Mode Rejection Specified Typically Only Specified at DC and Low Frequencies Common-mode rejection ratio (CMRR) is a differential probe s ability to reject any signal that is common to both test points in a differential measurement. This example shows the CMRR specifications for a 100 MHz high voltage differential probe The probe s bandwidth is 100 MHz but CMRR is only specified for DC, 50/60 Hz, 1 khz, and 1 MHz Where do you find CMRR characteristics for bandwidths higher than 1 MHz? 18

High Side Voltage Measurements on WBG HIGH SIDE V GS High Side V GS requires a probe with: Fast rise time capability Large common mode range High common mode rejection ALL AT THE SAME TIME 19

High Side Gate Measurements INTERACTION BETWEEN THE HIGH AND LOW SIDE Violation of specifications can cause: Simultaneous conduction Switching/efficiency loss Device degradation GaN devices have tight tolerances Parasitic coupling between switch node and both FETs 20

Can we use isolated probe systems? NOT ALL ISOLATED PROBES ARE CREATED EQUAL Isolated + high bandwidth + low impedance load + tailored to the application Also among Galvanic isolated systems, check for the specs to compare Today s GaN signals require to keep high CMRR up to 800MHz or more Probe CMTI and robustness to EMI disturbance is fundamental Flexibility design is important 21

What is IsoVu Technology? 1 GHz bandwidth (risetime <350ps) World s best Common Mode Rejection 2500 V differential voltage range at 60 kv CM range Up to 40 MΩ input resistance 6 DECEMBER 2017 22

Different Tip Connectors SHIELDING ALL THE WAY DOWN TO THE TEST POINT 6 DECEMBER 2017 23

Let s give a chance to TIVH08 ISOLATED PROBE AT WORK Issue #1: how do I connect to the component? 6 DECEMBER 2017 24

What else do I need to use IsoVu? EASY TO USE We can use IsoVu with usual Tek oscilloscope such as MDO/MSO IsoVu doesn t need external PC IsoVu doesn t need batteries Familiar user interface of MDO/MSO/DPO Accurate timing analysis with probe deskew Clamping circuit protecting scope from overdrive (on/off) 25

Influence of CMRR HIGH CMRR AND LOW INPUT CAPACITANCE OF ISOVU (TIVM1) Probing to floating point with shorted differential probe CH3: THDP0200 CH1: IsoVu + - CH1: IsoVu CH3: THDP0200 (Differential - Probe) + CH2: TPP1000 CH2: TPP1000 TIVM1 (IsoVu) 26

IsoVu has Wide Industry Adoption DESIGNERS ARE TURNING TO ISOVU TO REDUCE TIME TO MARKET AND VERIFY CRITICAL SPECIFICATIONS 27

BCI Immunity Test of Automotive LAN BULK CURRENT INJECTION Check transceiver operates rightly under Bulk Current Injection of 1MHz-400MHz Ground Plane Bulk Current Injection Probe RF Monitoring Probe Test in shield room 100Base-T1/1000Base-T1 CAN FD Transceiver 100Base-T1/ 1000Base-T1 CAN FD Transceiver From RF Injection (SG & Amplifier & Coupler) To Level Monitor (Spectrum Analyzer) 28

Recap LET S SUMMARIZE Adoption of wideband gap components into switching power topologies Half-bridge circuit is the building block of modern design topologies GaN and SiC based power converter require to rethink the measurement system, in particular the probing phase because we are blind when measuring the high side floating with current test solutions The combination of MSO 5 series oscilloscope and IsoVu probes provide capabilities that are not only best in class, but unique in the market 29

Thanks for joining! For further details: andrea.vinci@tektronix.com