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GaN Power System-in-Package
for efficient eMobility
Confidential information
▪ Expectation of GaN switches for high power applications:
from 6kW to 160kW
▪ Complications when reality meets expectations
▪ How to fulfill expectations using the package design and
functional partitioning
Outline
Confidential information
Expectation of GaN switches
▪ High Frequency Decrease magnetics size
▪ High Efficiency Cooling system would be simpler
▪ High Power Density Decrease footprint & weight
COMMON EXPECTATIONS
Small and lightweight GaN based system!
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Meeting with reality
▪ High Frequency High voltage & current spikes
▪ Reduced Frequency Again high voltage & current spikes
─ Increase trise/fall Increased power dissipation
▪ High power density Cooling system becoming complex
─ Increase # of transistors The whole system becoming expensive
COMMON COMPLICATIONS
GaN is amazing switch but end user did not gain much out of it…
Confidential information
How can we help
▪ Design the product to make life of designer easier
▪ Provide focused and customized support
▪ Make available relevant reference designs working for realistic
conditions
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How can we help
▪ Design the product to make life of designer easier
▪ Solve part of the system challenges by package level integration
Confidential information
Requirement # 1: high frequency
Challenges of high current ( 50 A to 200A ) high frequency
switching are:
1. Simple and robust drive for high frequency switching
2. Fast rise and fall times
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Requirement #1: Simple and robust drive for high frequency switching
▪ Two options could be considered for GaN:
▪ D-mode GaN requires negative voltage
▪ E-mode GaN has low VT and requires gate voltage swing from
negative to positive voltage
Confidential information
Requirement # 1: simple and robust drive
▪ Solution: Direct Drive circuit
▪ NOT a Cascode
▪ VT is + 5.5V , to be used with
standard drivers (like Si8239xISO)
with gate voltage 0V to +15V
VDD=+15V +15V
Gate signal: VG 0V to +15V
VGS (Q1) = -15V to 0V
Confidential information
Requirement # 1: simple and robust drive
▪ Solution: Direct Drive circuit
▪ NOT a Cascode
▪ With driver protection
▪ VT is + 5.5V , to be used with
standard drivers (like Si8239xISO)
with gate voltage 0V to +15V
VDD=+15V +15V
Gate signal: VG 0V to +15V
VGS (Q1) = -15V to 0V
Confidential information
Requirement # 1: simple and robust drive
▪ Solution: Direct Drive circuit
▪ NOT a Cascode
▪ With driver protection
▪ With Under Voltage Lock Out
▪ VT is + 5.5V , to be used with
standard drivers with gate voltage
0V to +15V
+15V
Gate signal: 0V to +15V
VGS (Q1) = -15V to 0V
VDD=+15V
Confidential information
Requirement # 2: Fast rise and fall times
▪ Challenge is in fast rise and fall times:→Requirements for
low inductance
Low inductance → low
voltage spikes
∆𝑉 = 𝐿 ×𝑑𝐼
𝑑𝑡
350 kHz HB buck
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Requirement # 2: Fast rise and fall times
▪ Low inductance: 2 nH
Leadless SMT packageHigh number of parallel wires
High number
of parallel
wires
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Requirement # 3: Over current protection
▪ Challenge: Avalanche voltage of GaN HEMT is well above
breakdown voltage of dielectrics → no avalanche
mechanism to release high current surge
▪ Solution: over current protection circuit
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Requirement # 3: Over current protection
▪ Challenge: provide noiseless current
sense
▪ Using LV MOSFET for current sense
reduces noise and improves
stability RDSON =1.5 mOhm
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Requirement # 3: Over current protection
▪ Solution: Over current
protection circuit
▪ Using LV MOSFET integrated
into the package
▪ Resulting in OCP circuit with
reaction time below 200 ns
GaN
GaN
Deadtime
control
UVLO
Isolation
Vref
Comp
Current sense
Vaux
Speed control
40nSec
40nSec
20nSec
135nSec
Current
Voltage on input of comp.
Current
Voltage on
input of comp.
Current Sense
Control circuit
Confidential information
Requirement # 4: Easy cooling solution
▪ Challenge: Heat transfer to a
heatsink for high power density
GaN die
▪ Solution: Low cost and high
thermal conduction EMPACK
solution. AlN ceramic under the
GaN die→ 2.4 kV isolation
Tθ = 0.3 K/W
No thermal pad is required;
2.5 kV isolated package
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Requirement # 4: Easy cooling solution
6kW @ 350kHz hard switching
buck converter
Midpoint Voltage
Inductor Current ≈25A
60°C TJ on High Side
Mid Point Voltage; 200V/div
TRISE=6.3 ns; TFALL= 7.8 ns
60⁰C
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Package level integration to ease system design
→ Low inductance
→ High & stable threshold
→ Over current protection
→ AlN-based EMPACK package
low voltage spikes @ fast
rise/fall time
use proven MOSFET driver
solutions
overcome avalanche
deficiency
low thermal resistance to
heat sink
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Couple of practical examples
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On-Board-Charger ref. design
21
▪ Smallest 6.7kW / 2.3L OBC available
▪ 3kW/L ➔ high power density
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Inverter mode: one V22N65ACA per 8 KW of delivered power
▪ FB CCM Hard switching; 80 kHz ; peak current IOUT(peak) = 52A
▪ TJ is below 50°C;
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Low voltage spikes
520V input voltage Buck hard switching @5kW 98.9%
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Right integration of low RDSON GaN die enables high
power density with high efficiency
Summary