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How to use GaN FETs

with Standard Power Supply ControllersNovember 2019

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Introduction

Andrea Mirenda

V.P. Americas Sales

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Efficient Power Conversion Corporation

• World’s largest supplier of GaN FETs and ICs for Power Conversion

• CEO – Alex Lidow– Co-Invertor of the modern power MOSFET

(HEXFET)– CEO of International Rectifier – 12 years

• Founded EPC in 2007

• eGaN FETs introduced in 2009

• Headquartered in El Segundo, CA

• Privately held

4www.epc-co.com

What is GaN-on-Si?

GaN-on-Si is…

EPC’s eGaN® Technology is the undisputed industry leader

• Faster

• Smaller

• More Efficient

• Cost Effective

• Easier to Integrate

• More Reliable

…as compared to Silicon

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EPC’s Focus is 400 V and Below

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Where is GaN Used?

• DC-DC Converters

• Laser Driver for LiDAR

• Wireless Power Transfer

• High Density AC Adapters

• High Precision Motors

• Automotive LED Headlights

• Space Applications

• LED Lighting

• Medical Applications

• Class D Audio

• Cellular Base Stations

Small size and high efficiency at high frequency

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Adoption Checklist

Best performance?

YES

Reliable?

YES – automotive certification and field experience.

Cost Effective?

YES – system and component optimization

Availability?

YES – eGaN devices available from stock to 10 weeks

Easy to use?

multiple driver ICs available

More qualified engineers in the design pool

Monolithic Half Bridge will eliminate much design and assembly engineering

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• Conferences– APEC, CES, IEEE, PCIM EU/AP, PCB Carolina,

Application Specific events

• Social Media– Linked In, GaN Talk Blog,

• Mail list for PR, NPI, Events etc• Articles, white papers, Design Tips, Books,

Videos• Digi-Key Supplier Portal

– https://www.digikey.com/en/supplier-centers/e/epc

• EPC You Tube Channel https://www.youtube.com/user/EPCCorporation

Keeping Updated With EPC

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EPC’s Strategy

• Deploy GaN-on-Si for power conversion

• Manufacture products

– using existing silicon infrastructure for low cost

– high quality

– high capacity potential

• Integrate discretes and ICs to improve performance and reduce design cost

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Using GaN FETs

Brian Miller

Field Applications Engineer

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2019: What is New at EPC

• 100 V pin-compatible family

• Automotive Approval

• Reference Designs using existing Controller ICs

• Web-based GaN FET Selection Calculator

• In Development: Monolithic half-bridge GaN with Gate Driver

• Reference designs

• Thermal Design Note

EPC – The Leader in GaN Technology www.epc-co.com

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EPC’s GaN FETs & ICs

• Power FETs and ICs:– 15 V to 350 V, 0.5 to 90 amps

– Gate drive: 5V = on, 0V = off

• Extremely low capacitance and inductance

• Zero Reverse Recovery (QRR)

• Reduces system size and cost– Smaller devices

– Higher frequency reduces capacitor, inductor, etc. size

• Enables new products– Such as LiDAR

• Reliable– > 80 B device hours in the field

EPC2036:

• 100 V

• 1.7 A

• 0.9 x 0.9 mm

coming soon:

Integrated Gate

Driver Half Bridge

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Fundamental Advantage

GaN gives a smaller device with lower RDS(on)– Lower capacitance

• Faster voltage commutation

• Lower loss switching

– Lower inductance• Faster current commutation

• Lower EMI

– Zero QRR

• Lower Switching losses

200 V eGaN FET

(25 mΩ)

200 V Silicon Device

(30 mΩ)

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Designing with GaN FETs

Differences between GaN FETs and Silicon

MOSFETs for Power Supply Design:– Gate Voltage

• GaN: 0V off, 5V (6V max) on

• Si MOSFETs: 0V off, 12-20V max. on

– No Reverse Recovery in GaN FETs

• Short dead time is allowed

– Diode drop higher

• About 2-3 V,

• So, careful of negative voltage on switch node

• May need a small Schottky in parallel

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Design Example: Boost

Example: Maxim MAX17292– 5 V gate drive

– Up to 2.5 MHz

– Be careful with current sense R

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Design Example: Flyback

Transformer-coupled output:– Example: MAX17597 has 5V gate drive

– May add gate series resistor

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Design Example: Buck Converter

Synchronous buck converter:– Most common for power supplies

– GaN Advantages• Smaller FETs

• Higher efficiency

• Higher frequency for smaller passives

– Need to• Control negative voltage during dead time

• Limit boosted voltage

• Dead time may be long

• Insure dv/dt is OK

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Using Controllers designed for

MOSFETs with GaN FETs

• Don’t need to use GaN-specific controllers• Do need to keep gate below 6V

From LT’s LTC7800 data sheet, page 29, Fig. 14

Example: LTC7800• R: in series with the boost diode to

limit current• Assumes external boost diode

• D3 = 5.1V Zener, in this case Bourns CD0603-Z5V1

• D2 = small Schottky diode, in this case Diodes, Inc. DFLS2100

• Works for many other controllers if:• 5V gate drive, or can set to 5V,

or external 5V source• Dv/dt is OK, or slow down with

Rgate.

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EPC board: EPC9141

– Uses LTC7800 controller (just

one of many possible controllers)

– This board pre-set for 48V input,

12V output, 360 kHz, 10A output

– 15 A version: EPC9138, 320 kHz

– Controllers: LTC7800, TI’s

LM5141, etc. can be externally

modified to work with EPC’s

eGaN FETs

EPC Reference Designs

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https://epc-co.com/epc/Products/DemoBoards/EPC9141.aspx

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EPC board: EPC9141

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https://epc-co.com/epc/Products/DemoBoards/EPC9141.aspx

EPC Reference Designs

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Design Example: Digital Controllers

– Programmable Microcontrollers

– Advanced control of power supplies

uCDual Gate

Driver

GaN FET

GaN FETExamples:

– TI LMG1205, LMG1210

– uPI uP1966A

– Silicon Labs Si827x

– ON Semi NCP51820

– P-Semi PE29102

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co-packaged Drivers + GaN FETs

– Fewer Parts

– Layout Optimized

uCDual Gate

Driver

GaN FET

GaN FET

TI’s LMG5200

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Integrated all-GaN Driver/FETs

– Coming in Spring 2020

– Fast, Efficient, and Layout Optimized

– 80 V, 1 MHz, 10 A

– 2.6 x 3.9 mm

uCDual Gate

Driver

GaN FET

GaN FET

EPC2151 & EPC2152

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Phase 3: Monolithic HB + Drivers

Features– Monolithic HB + Drivers

– 10 A, 80 V, 1 MHz

– More efficient than discretes

• Benefits• Reduced design and

assembly costs

• High efficiency

• Small Size

• Competitive system cost

3.9 mm

2.6

4 m

m

EPC2151: 21 & 7 mΩ

EPC2152: dual 10 mΩ

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Die Size Optimization

Optimal

Performance

Price (die size for a given process)

Acceptable

Performance

Perf

orm

ance

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1 E-04

1 E-03

1 E-02

50 500 5000

RD

S(o

n),

SP

(Ω·c

m2)

Breakdown Voltage (V)

Theoretical Channel Resistance

Why eGaN® FETs?Highest Semiconductor Performance Possible

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Ultra-Fast Switching

VIN=12-28 V VOUT=3.3 V

IOUT=15 A FS=1 MHz

2 x EPC2015C

5 V/ div

Switching Node

Voltage VIN=28 V IOUT=15 A

Little ringing for low EMI

VIN=28 V~3V overshoot @ 15 Aout

20ns

~1.1ns rise time @ 15 A

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Stable over Temperature

0.6

0.7

0.8

0.9

1

1.1

1.2

0 25 50 75 100 125 150

No

rmali

zed

Th

resh

old

Vo

ltag

e

Junction Temperature ( C)

eGaN FET

Si MOSFET

• Gate Threshold stability over temperature

provides precise, consistent switching

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Total Gate Charge

0

1

2

3

4

5

6

7

8

9

10

0 10 20 30 40 50 60 70 80

VG

S(V

)

QG (nC)

VGS vs QG

EPC2022 – 100 V, 3.2 mΩ

BSC035N10NS5 – 100 V, 3.5 mΩ

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Higher Performance - 100 V FETs

84

85

86

87

88

89

90

91

92

93

94

95

96

0 2 4 6 8 10 12 14 16 18 20 22 24 26

Eff

icie

nc

y

Output Current (A)

fsw=500 kHz

VIN=48 V VOUT=5 V

EPC2001C Gen 4

BSZ097N10NS5

EPC2045 Gen 5

EPC2045 Generation 5

Comparable RDS(on)

Gen 5 Devices have higher performance and are about half the size of Gen 4.

Both are far superior to the best available MOSFET

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Part number Vds Rdson Id-A Rthjc Rthjb Rthja Area PackageVolts mohm A deg C/W deg C/W deg C/W Sq. mm

BSC030N08NS5 80 3 100 20 0.9 50 30 PQFN56EPC2021 80 2.5 90 0.4 1.1 42 13.92 LGA

Active GaN Region

Silicon Substrate

Heat Flow Path• Double side cooling device. • RθJC (to the top) is much lower

than RθJB (to board). • more heat removed from

junction through top Si.• with heat sink attached

• Die Perimeter helps in removing the heat from the junction

• Allows device to run cooler• Carry more current

Thermal Paths in eGaN FETs

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Thermal Management for Flip Chip

HEATSINK

RθJc

RθJB

TIM

RθHARθHA

RθTIMRθTIM

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Thermally Efficient

0

0.5

1

1.5

2

2.5

3

0 5 10 15 20 25 30 35

RƟJB,T

herm

al

Resis

tan

ce (°

C/W

)

Device Area (mm2)

RθJB_Si

RθJB_Ga

N

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Dual Sided Cooling

0

0.5

1

1.5

2

2.5

3

0 5 10 15 20 25 30 35

RƟJC, T

herm

al

Res

ista

nc

e (°

C/W

)

Device Area (mm2)

RθJC_Si

RθJC_G

aN

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DC/DC: 48 V to 12 V

Lower On Resistance

Faster

Less Capacitance

Smaller

Lower Cost

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LiDAR

EPC’s eGaN FETs:

– Fast

– High Current Pulses

– Small

LiDAR

evaluation

board EPC9126

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Brushless DC Motor Drive

• Efficient, high PWM frequency operation with:

• Reduced QGD

• Reduced QOSS

• Zero QRR

• Higher PWM frequency allows reduced motor

inductance.

• Reduced motor inductance allows reduction

in copper and iron size, weight, and cost.

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Wireless Power

Resonant: 6.78 or 13.56 MHz

Amplifier

Impedance

Matching

Network +

Supply Source

Source

CoilRectifier

Device

Coil

Load

Impedance

Matching

Network

Device

EPC’s eGaN FETs:

– Efficient/Cool

– High Power

• 100 W +

– Small

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Audio: Class D Amplifiers

EPC’s eGaN FETs:

– Precise Reproduction of Sound

• Better than most liner amplifiers

– Efficient/Cool

• Often needs no heat sink

– Higher Frequency is Possible

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Wafer Level Packaging

Fewer interconnects

Smaller, Simpler

Better Performance

Compatible with small outline, surface mount manufacturing

Source/Gate Clips

Source/Gate Die Attach

MOSFET Die

Drain Die Attach

PCB

PCB Gate

ConnectionPCB Source

Connection

PCB Drain

Connection

GateSource

Drain Pad

MOSFET

eGaN FET Die

Drain/Source/Gate

Connections

PCB

PCB Source

ConnectionPCB Gate

Connection

PCB Drain

Connection

eGaN FET

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EPC has over 45 discrete transistors and ICs available for

off-the-shelf delivery

Proven Reliability – 6 years and over 30 billion device

hours in the field with only 3 device failures.

Proven Product Portfolio

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EPC Resources & Support

• Comprehensive Web with• Device specifications and models• Application notes• Reliability data

Design Review & Layout Support

• Demo Boards • We share Gerber files,

schematics, and BOM for ease of adapting the design

Digi-Key availability at time of release

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Very Complete

Web Site

• epc-co.com

• many links

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Product Selection Tool

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• EPC is the global leader in GaN-on-Si

• GaN technology is improving rapidly

• EPC has demonstrated eGaN technology reliability in the lab and in the field

• eGaN integration significantly improves performance and lowers design cost

Summary