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![Page 1: APEC 2020 Industry Sessions - we-online.com · Buck-Boost Automotive USB-PD Type C –14VIN 350kHz 20V 3A PDO (Boost) and 9V 3A PDO (Buck) 350kHz fsw for this application SSFM Run](https://reader034.vdocuments.mx/reader034/viewer/2022042420/5f378ad6c04bd46c622da758/html5/thumbnails/1.jpg)
Hebberly Ahatlan
Product Marketing Manager Analog Devices
Keith Szolusha
Sr. Applications Manager Analog Devices
Quentin Laidebeur
Team Lead Product Definition Engineering America
APEC 2020
Industry Sessions
5 March 2020 ©2020 Analog Devices, Inc. All rights reserved.1
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Practical DC/DC EMI
improvement
techniques
Understanding the inductor’s EMC role at the
switching node
©2020 Analog Devices, Inc. All rights reserved.2 5 March 2020
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Introduction
It is well understood that a power MOSFET in a SMPS
contributes high voltage ringing that propagates across traces
and components and causes compatibility issues.
5 March 2020 ©2020 Analog Devices, Inc. All rights reserved.3
V
Simplified Boost DC/DC
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A typical conducted path for the MOSFETs noise is the switching
side of the inductor.
5 March 2020 ©2020 Analog Devices, Inc. All rights reserved.4
V
Simplified Boost DC/DC
Introduction
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Since the inductor output lead and the switching node are
practically the same point in most designs, the inductor can be
both a victim of the MOSFET noise and an amplifier of it.
5 March 2020 ©2020 Analog Devices, Inc. All rights reserved.5
V
Simplified Boost DC/DC
Introduction
![Page 6: APEC 2020 Industry Sessions - we-online.com · Buck-Boost Automotive USB-PD Type C –14VIN 350kHz 20V 3A PDO (Boost) and 9V 3A PDO (Buck) 350kHz fsw for this application SSFM Run](https://reader034.vdocuments.mx/reader034/viewer/2022042420/5f378ad6c04bd46c622da758/html5/thumbnails/6.jpg)
5 March 2020 ©2020 Analog Devices, Inc. All rights reserved.6
V
Simplified Boost DC/DC
To mitigate this SW node noise we can attempt any combination
of these three solutions:
Change the layout
Change the inductor
Shield the noise node
In this presentation we will explore each of these
methods and offer tips along the way to optimize
them.
Introduction
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Changing the
layout
Tips on changing layout to improve inductor immunity
©2020 Analog Devices, Inc. All rights reserved.7 5 March 2020
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Identifying Parasitic Antennas
5 March 2020 ©2020 Analog Devices, Inc. All rights reserved.8
Long traces on a board can
interact with the inductor
L
Fsw
Is λ of Fsw = L~ 1/2𝑛𝑛 = 𝑤ℎ𝑜𝑙𝑒 𝑛𝑢𝑚𝑏𝑒𝑟
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The effects of via and trace orientation
5 March 2020 ©2020 Analog Devices, Inc. All rights reserved.9
Direction of H-field affects
magnetic coupling among
nearby components
Fsw H
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Repositioning traces and planes
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Distance and surface area
affect field coupling
Fsw
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USB-PD Type C Buck-Boost Automotive Charger
Feburary 4, 2020 Analog Devices Highly Confidential Information. ©2020 Analog Devices, Inc. All rights reserved.11
Inductor Orientation 1
Short-Terminal on Buck-SW Side
Inductor Orientation 2
Short-Terminal on Boost-SW Side
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Buck-Boost Automotive USB-PD Type C – 14VIN
350kHz 20V 3A PDO (Boost) and 9V 3A PDO
(Buck)
► 350kHz fsw for this application
► SSFM
► Run CISPR 25 emissions testing with L1 6.8 uH inductor in two different assembly orientations.
Does it matter which way it is assembled?
► Check Radiated and Conducted Emissions – Peak and Average
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-10
0
10
20
30
40
50
60
0.1 1 10 100 1000
AV
ER
AG
E R
AD
IAT
ED
EM
ISS
ION
S [d
Bµ
V/m
]V
ER
TIC
AL
PO
LA
RIZ
AT
ION
FREQUENCY [MHz]
-10
0
10
20
30
40
50
60
0.1 1 10 100 1000
AV
ER
AG
E R
AD
IAT
ED
EM
ISS
ION
S [d
Bµ
V/m
]V
ER
TIC
AL
PO
LA
RIZ
AT
ION
FREQUENCY [MHz]
Inductor Has Best Emissions When Short
Terminal is Placed on Active SW Node.
Feburary 4, 2020 Analog Devices Highly Confidential Information. ©2020 Analog Devices, Inc. All rights reserved.13
L1 Orientation 1
L1 Orientation 2
CISPR25 Limits Class 5
14VIN 20VOUT 3A (60W)
2-SW BOOST
14VIN 9VOUT 3A (27W)
2-SW BUCK
Radiated Emissions
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-50
-30
-10
10
30
50
0.1 1 10 100
AV
ER
AG
E C
ON
DU
CT
ED
EM
I [d
BµA
]750m
m
FREQUENCY [MHz]
-50
-30
-10
10
30
50
0.1 1 10 100
AV
ER
AG
E C
ON
DU
CT
ED
EM
I [d
BµA
]750m
m
FREQUENCY [MHz]
Inductor Has Best Emissions When Short Terminal
is Placed on Active SW Node.
Feburary 4, 2020 Analog Devices Highly Confidential Information. ©2020 Analog Devices, Inc. All rights reserved.14
L1 Orientation 1
L1 Orientation 2
CISPR25 Limits Class 5
14VIN 20VOUT 3A (60W)
2-SW BOOST
14VIN 9VOUT 3A (27W)
2-SW BUCK
Conducted Emissions – Current Probe
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-20
-10
0
10
20
30
40
50
60
70
80
0.1 1 10 100
AV
ER
AG
E C
ON
DU
CT
ED
EM
I [d
BµV
]
SU
PP
LY
FREQUENCY [MHz]
-20
-10
0
10
20
30
40
50
60
70
80
0.1 1 10 100
AV
ER
AG
E C
ON
DU
CT
ED
EM
I [d
BµV
]
SU
PP
LY
FREQUENCY [MHz]
Inductor Has Best FM Band Voltage CE When Short
Terminal is Placed on Active SW Node.
Feburary 4, 2020 Analog Devices Highly Confidential Information. ©2020 Analog Devices, Inc. All rights reserved.15
L1 Orientation 1
L1 Orientation 2
CISPR25 Limits Class 5
14VIN 20VOUT 3A (60W)
2-SW BOOST
14VIN 9VOUT 3A (27W)
2-SW BUCK
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Buck-Boost Automotive USB-PD Type C – 14VIN
400kHz 20V 3A PDO (Boost) and 9V 3A PDO
(Buck)
Result Summary:
► Inductor orientation makes a very significant impact on CISPR 25 emissions results
► The best emissions in boost operation (20V output) occur when the short-side terminal is assembled
on the boost SW.
► The best emissions in buck operation (9V output) occur when the short-side terminal is assembled
on the buck SW.
Feburary 4, 2020 Analog Devices Highly Confidential Information. ©2020 Analog Devices, Inc. All rights reserved.16
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05.03.2020 17
Changing the
inductor Tips on changing inductors to mitigate radiated compatibility
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05.03.2020 18
Start of Winding Effect on EMI
Performance
Multiple layer Inductors Single layer Inductors
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05.03.2020
Inductor Material Effect
19
-Iron Powder
-Soft saturation
-Good Shielding
-Ferrite
-Hard saturation
-Good Shielding
-High Permeability Alloys
-Medium saturation
-Good Shielding
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05.03.2020
Inductor Construction and
Winding Orientation
20
Gapped construction / Flat wire
VerticalGapped construction / Round wire
Horizontal
Distributed gap / Flat wire
Vertical
TO
P V
IEW
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Shielding the noise
source
Tips on the benefits and drawbacks of shielding
©2020 Analog Devices, Inc. All rights reserved.21 5 March 2020
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Types of shielding
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©2020 Analog Devices, Inc. All rights reserved.23 5 March 2020
LED Driver Prototype PCB – 12VIN 250kHz
45V 500mA LED String
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LED Driver Prototype PCB – 12VIN 250kHz 45V
500mA LED String
► Low EMI Silent-Switcher Monolithic 60V 3A IC with High Dimming Ratio
► 2-SW Synchronous Boost LED Driver
► 250kHz fsw for this application
► SSFM
► Run CISPR 25 emissions testing with two different shields to see if the solid shield is more effective
than the shield with holes in it.
► Shield is clipped onto PCB
► Shield is effective to pass very low emissions requirements for certain customers.
Feburary 4, 2020 Analog Devices Highly Confidential Information. ©2020 Analog Devices, Inc. All rights reserved.24
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Buck-Boost USB-PD Type C – 14VIN 400kHz 20V
3A PDO (Boost) and 9V 3A PDO (Buck)
Result Summary:
► Both shields act the same.
► Further work is required to see if soldering a shield directly to the PCB ground is more effective than
using clips.
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Both Shields Reduce the Already Low Radiated
Emissions Above 10MHz
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No Shield
Standard Shield With Holes
Solid Shield With No Holes
CISPR25 Limits Class 5
Both Shields Have Similar Results
Red and Green Shield Plots Are Equal
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Both Shields Reduce the Already Low Current
Probe Conducted Emissions Where it is Critical
Feburary 4, 2020 Analog Devices Highly Confidential Information. ©2020 Analog Devices, Inc. All rights reserved.27
No Shield
Standard Shield With Holes
Solid Shield With No Holes
CISPR25 Limits Class 5
Both Shields Have Similar Results
Red and Green Shield Plots Are Equal
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Both Shields Reduce the Already Low Current
Probe Conducted Emissions Where it is Critical
Feburary 4, 2020 Analog Devices Highly Confidential Information. ©2020 Analog Devices, Inc. All rights reserved.28
No Shield
Standard Shield With Holes
Solid Shield With No Holes
CISPR25 Limits Class 5
Both Shields Have Similar Results – Need > LC Input Filter
Red and Green Shield Plots Are Equal
![Page 29: APEC 2020 Industry Sessions - we-online.com · Buck-Boost Automotive USB-PD Type C –14VIN 350kHz 20V 3A PDO (Boost) and 9V 3A PDO (Buck) 350kHz fsw for this application SSFM Run](https://reader034.vdocuments.mx/reader034/viewer/2022042420/5f378ad6c04bd46c622da758/html5/thumbnails/29.jpg)
LT8386 HUD LED Driver
Feburary 24-28, 2020 Analog Devices Highly Confidential Information. ©2020 Analog Devices, Inc. All rights reserved.29
► Shield mount
► Output caps and hot-
loop caps testing
► PWM switch and filter
► Input filter
AM band
All frequencies
► 250-400kHz applications
(preferred by customer)
► Silent Switcher 1
► LT8386 or LT3922-1
► EMI filters
► 10k:1 150Hz PWM Dimming
9-16VIN
With output filter
50k:1 PWM dim with no filter
► 4k:1 1kHz Daimler Spec
► Shield mount and tested
► 45V 500mA LEDs
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Conclusions and
Q&A
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Contact ADI or Wurth for
more information
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Hebberly Ahatlan
Product Marketing Manager Analog Devices
Keith Szolusha
Sr. Applications Manager Analog Devices
Quentin Laidebeur
Team Lead Product Definition Engineering America
Thank you
5 March 2020 ©2020 Analog Devices, Inc. All rights reserved.32