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82
15.0
80
14.5
78
14.0
76
13.5
74
70
13.0
η eGaN FET
η MOSFET
72
12.5
Pout eGaN FET
Pout MOSFET
10
15
20
25
30
35
40
DC Load Resistance [Ω]
45
50
12.0
TECH SERIES
Output [W]
Efficiency [%]
CONTENTS
CONTENTS
Wi GaN
Wireless Power Amplifier Comparison
Figure 3: Load variaAon eﬃciency of MOSFET and eGaN FET in a class E wireless power ampliﬁer Understanding Soft Errors
in Semiconductor Memory
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TECH REPORT
DESIGN CHALLENGES
DESIGN SOLUTIONS
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TECH SERIES
Wi GaN:
A Comparative Analysis of Class E
and ZVS Class D Amplifiers for Use in
Wireless Power Transfer Systems
Wireless power transmission is one of the fastest growing
applications in both consumer and industrial electronics. As
embedded systems within both transmitting and receiving
devices, it is crucial for power system designers to understand the
fundamental system design and the components contributing to its
performance. There are three main constituents of a wireless power
system with the amplifier, a transmit coil, and a receive coil typically
housed within a receiving device as shown in figure 1 [1].
By Bhasy Nair, Director of Global
Field Applications Engineering and
Michael A. de Rooij, Executive
Director of Applications Engineering,
Efficient Power Conversion (EPC)
8
9
Wireless Power Amplifier Topologies
Selecting a standard to which to design an
amplifier is the first task, since each standard
requires a different power architecture and
communications protocol. Over the past several
years, three standards for wireless power have
emerged – the Wireless Power Consortium’s Qi,
the Power Matters Alliance [10] and the Alliance
for Wireless Power (A4WP), also known as
Rezence® [2].
The Rezence standard centers on the highly
resonant loose-coupling approach that allows
much larger distance and spatial freedom
between transmit and receive units. The
operating frequency of Rezence standard is
6.78MHz, which is part of the ISM Band. The two
most popular amplifier topologies for resonant
power transfer are class E and ZVS class D.
Both topologies yield high performance, but for
Class E amplifiers special low capacitance high
voltage MOSFETs are required to accomplish
operation at this high frequency. Replacing
the silicon-based power MOSFET with an
enhancement-mode gallium nitride eGaN
FET [3], the losses in a Class E amplifier can be
reduced by 20%. This decrease in losses is due
to the lower gate capacitance and on-resistance
of the GaN FETs relative to MOSFETs for similar
output capacitance and voltage rating. Thus,
they require and dissipate less energy. In turn,
this means that GaN FETs can operate at higher
frequencies resulting in higher performance
capability for the amplifier. The ability to
switch at higher frequencies is critical for the
implementation of the Rezence.
characteristics of eGaN FETs, with their smaller gate
and drain capacitances, reveal that the losses in the
eGaN FET amplifier are about 20% lower, allowing
for a 5% increase in efficiency over a power MOSFET
based amplifier.
One major setback of the class E amplifier is that
the output power and efficiency rapidly roll off
as the output DC load increases, and shown in
Figure 3. This roll-off condition needs to be
corrected by complex and expensive matching
circuits that can adapt to the changing load
conditions [4].
ZVS Class D Amplifier for Wireless Power Transfer
ZVS class D amplifier topologies avoid the rapid
roll-off and provide a higher and flatter efficiency
over the entire load range. The ZVS class D amplifier
is a modified class D design (shown in figure 4)
that uses an “LC tank” (ZVS tank) circuit. This ZVS
tank ensures that the FETs switch at or near zero
voltage, even with variations in load conditions,
thereby avoiding the output power and efficiency
roll off seen with class E amplifiers [5].
Limitations of Class E Amplifier: Rapid
Roll Off of Efficiency and Output Power
Silicon power MOSFETs are commonly used in
class E amplifiers such as the one shown in
figure 2. The gate charge of MOSFETs are much
higher than that of a eGaN FET and the higher
drive power required for MOSFTs has a major
impact on the overall efficiency of the system.
As shown in Figure 2, the superior switching
Figures 5(a) and 5(b) show the comparison of the
efficiency and load curves of both amplifiers [2].
82
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80
14.5
78
14.0
76
13.5
74
70
13.0
η eGaN FET
η MOSFET
72
12.5
Pout eGaN FET
Pout MOSFET
10
15
20
Output [W]
At the heart of the wireless power system is the
amplifier—identifying the best amplifier topology
and most efficient components is the focus of
this article. Distinguishing attributes of a good
amplifier such as EMI, load impedance drive
range, and the ability to operate in accordance
with multiple standards will be addressed.
Efficiency [%]
TECH SERIES
25
30
35
40
DC Load Resistance [Ω]
45
12.0
50
Figure 3: Load variation efficiency of MOSFET and eGaN FET in a class E
Figure : Load variaAon eﬃciency of MOSFET and eGaN FET in a class E
wireless 3
power
amplifier.
wireless power ampliﬁer VDD
Q2
ZVS tank
CS
LZVS
Q1
ZLoad
CZVS
Figure 4: ZVS class D amplifier.
Figure 4: ZVS class D ampliﬁer. V/I
VDD
Amplifier
Source
Impedance Coil
Device
Coil Impedance
Matching
Network
Supply
Matching
Network
3.56 x VDD
LRFck
Rectifier
Le
Load
Csh
Source
Device
CS
ID
VDS
Q1
Figure 1:pWireless
system
components—
Figure 1: Wireless ower spower
ystem with with
components – source, ampliﬁer, and device Figure 2: Class E amplifier.
source, amplifier, and device.
Figure 2: Class E ampliﬁer 10
ZLoad
50%
Ideal Waveforms
Time
Figure
5(a):4 Class
E amplifier
efficiency
andaEnd power
Figure (a) Figure Class E4 A(a) mplifier Class EE fficiency Amplifier fficiency and output as DC output load changes.
utput s load output s load changes. Figure 5Figure (a): power Class 5o(a): Epower aCampliﬁer lass Echanges. aampliﬁer eﬃciency eﬃciency and power and oputput ower o
as utput DC as DC output output load changes load changes 5(b): ZVS Class D amplifier efficiency and
Figure Figure
4 (b) Figure ZVS CD 4 (b) Amplifier ZVS CD E fficiency Amplifier aEnd fficiency and power output as DC output load changes.
power utput power as Z
load oVS utput hanges. as load Figure 5Figure (b): ZoVS 5(b): Class Dc C
alass mpliﬁer Dc hanges. ampliﬁer eﬃciency eﬃciency and power and oputput ower o
as utput as DC output DC o
load utput changes load changes 11
TECH SERIES
Environmental Impact and Compliance
There are several operating conditions that can
affect a wireless power system, such as; the (1)
distance between the source coil and the receive
coil, (2) position of the source coil relative to the
receive coil, (3) placement of multiple devices on
the source coil and (4) the introduction of a solid
metal object to the source coil. All these factors
will lead to changes in the effective coupling
between the source coil and the receiving device
coils. This causes the coil impedance to shift
from the ideal resonance operating point, by
increasing or decreasing both the real and reactive
components of the load causing a de-tuning
effect and adversely impacting the performance
of the system.
Changes in Impedance
Figure 6 shows the efficiency for both the class
E (red) and ZVS class D (blue) amplifiers using
eGaN FETs operating through a range of reflected
load reactances plotted for various reflected load
resistances. Again, it is noteworthy that the ZVS
class D amplifier exhibits a relatively flat efficiency
over the entire impedance range compared to class
E, except at resonance points, demonstrating the
stable performance of ZVS class D amplifier [5].
98
Efficiency [%]
In order to achieve operation over the entire
impedance range of a Class 3 PTU, retuning
of the coil is needed which is accomplished
by changing the value of the tuning capacitor.
The automated process of doing this is called
adaptive matching. A single retuning adaptive
matching cell is comprised of a back-to-back
high voltage low RDS(on) FET switch (shown in the
gray boxes in Figure 8) that is connected in series
with the appropriate parallel tuning capacitor to
420V
retune the coil. A multi-bit adaptive switching
350V
280Vretuning
circuit is. comprised of multiple of these
210V
140V
cells capable of retuning the coil to within
70V the
0V
amplifier capability in discrete steps. Depending
-70V
Since the operational range capability of the ZVS
class D amplifier is wider than that of class E
amplifier as shown in Figure 6, a smaller number
of discrete matching circuits (cells) will be needed
to retune the ZVS class D amplifier in order to
bring it within the amplifier capability. This results
in a lower cost and a more attractive system
solution for wireless power transfer, particularly
at higher power (> 16W).
V(Coil)
EMI Generation Comparison Between
Class E and ZVS Class D
To understand the difference in EMI generation
between the class E and ZVS class D amplifiers,
420V
I(Lcoil)
1.2A
350V
both will be simulated in LTspice
[7]
when
1.0A
280V
0.8A
210V
operating to deliver 14W into
0.6A an A4WP
140V Class
0.4A
70V
3-compliant load. Figure 90.2Ashows the simulation
0V
0.0A
-70V
-0.2A
-140V
results of the EMI content-0.4Aof the current
-210V
-0.6A
-0.8A
-1.0A
2 f0
4 f0
0db
-20db
20db
0db
-20db
92
-40db
f0
-60db
ZVS-CD 55 Ω, 16 W
88
SE-CE 55 Ω, 16 W
-80db
SE-CE 36 Ω, 16 W
-100db
-30 -25 -20 -15 -10 -5
0
5 10
Imaginary Impedance [Ω]
15
20
-80db
Figure 5. Impact of imaginary part of impedance on efficiency Figure
6: Efficiency
impact iof
reflected
variations
on both
the classoEn (red)
Figure 6: Eﬃciency mpact of load
reﬂected load variaAons both and ZVS class D amplifiers (blue) driving an A4WP class 3 compliant load.
the class E (red) and ZVS class D ampliﬁers (blue) driving an A4WP class 3 compliant load -100db
CS2
CS3
I(Lcoil)
-280V
-350V
-420V
0ns
60ns
Amplifier Connection
QSn
Additional
Cells
Gate
Driver
QS2
V(Coil)
QS4
Gate
Driver
QSm
I(Lcoil)
1.2A
1.0A
0.8A
0.6A
0.4A
0.2A
0.0A
-0.2A
-0.4A
Figure 8: Multi-bit adaptive matching network
-0.6A
-0.8A
-1.0A
-1.2A
180ns
240ns
300ns
360ns
420ns
480ns
540ns
Figure 8: MulA-‐bit adapAve matching network 120ns
2 f0
4 f0
V(Coil)
4 f0
I(Lcoil)
0db
40db
0db
QS3
Gate
Driver
CS1
CSn
-20db
f0
f0
-40db
-20db
f0
-60db
-60db
-80db
-80db
-100db
-100db
-120db
-120db
-140db
LCoil
-40db
-60db
ZVS-CD 36 Ω, 16 W
4 f0 2 f0
60db
20db
-40db
90
CS
QS1
40db
94
86
Adaptive matching will also improve coil
efficiency as it effectively narrows the impedance
range of the coil and brings it back to operate
closer to resonance.
V(Coil)
60db
waveform for a single-ended class E and singleended ZVS class D amplifier. Notice that the
even order harmonics are absent in the current
waveforms for ZVS class D whereas these
harmonics are present in the class E amplifier.
Even-order harmonics impact fundamental
asymmetrically and are extremely difficult to
filter out. Since the ZVS class D amplifier has
almost zero even harmonic content in the
spectrum, EMI compliance becomes less of an
issue compared to a class E amplifier [8].
on the reflected load impedance change, the
adaptive matching controller will activate the
appropriate cell to get the coil back to resonance.
-140V
-210V
-280V
-350V
2 f0
Total Amplifier Efficiency
96
12
Adaptive Tuning for Optimizing Performance
Figure 7 shows the range of impedance capability
of both class E and ZVS class D amplifiers, on
a Smith Chart® for a A4WP standard Class
3 source load. The shorter purple dashed arc
arrow shows the class E amplifier range and the
longer red dashed arc arrow shows the ZVS class
D amplifier range. It is clear from the chart that
neither of the amplifiers are capable of operating
over the entire impedance range of a Class 3
Power Transfer Unit (PTU), represented by the
area shaded in blue [6].
10MHz
100MHz
Voltage
Figure 7: Class E and ZVS class D amplifier impedance
capability
superimposed
the
class
3 standard.
Figure 6. S-‐parameter chart owith
f Class 3 rA4WP
esonator superimposed
Figure 7: Class and VS class mpliﬁer impedance with E
Class E aZnd ZVS class D
D ia
mpedance range
capability superimposed with the A4WP class 3 standard 1GHz
-140db
-120db
-120db
-140db
10MHz
10MHz
100MHz
100MHz
Current Voltage
Figure 9(a): EMI content of current waveform Class E.
Figure 9(a): EMI content of current waveform Class E 1GHz
1GHz
-140db
10MHz
100MHz
1GHz
Current
Figure 9(b): EMI content of current waveform Class ZVS Class D.
Figure 9(b): EMI content of current waveform Class ZVS Class D 13
TECH SERIES
Multi-mode Wireless
Power Transfer Capability
The rising demand for wireless power for a range
of mobile devices, such as tablets, laptops and
even power tools, together with the multitude
of wireless power transfer standards (i.e., Qi, PMA
and Rezence) [9–11] serves to hinder adoption of
this technology, as it leads to end-user confusion
and loss of inter-operability. The Qi and PMA
standards operate at much lower frequencies
(<315kHz) compared to Rezence operating at
6.78MHz and a single multi-mode amplifier that
can transfer power regardless of the standard
used by the receiving device is needed.
Amplifiers designed in accordance with the
Qi and PMA low frequency operation cannot
typically support operation at 6.78MHz operation
required for the Rezence platform. Thus, in order
for a MOSFET-based amplifier to support the
three standards at least two sets of converters
and two resonator coils will be required, making
this solution cost prohibitive and bulky. The
class E topology uses the FET in a resonant mode
at 6.78MHz and hence adopting it for a much
lower frequency for Qi or PMA is not a
practical solution.
The ZVS class D topology amplifier can easily
be modified to work as a multi-mode power
converter, as shown in Figure 10. With Q3 turned
off to isolate the ZVS tank circuit, the half bridge
(Q1 and Q2) can be used to support Qi or PMA
mode. With Q3 turned on to connect the ZVS
tank circuit to the output of the amplifier, the
same amplifier can now operate as a ZVS class D
amplifier at 6.78MHz to drive Rezence standard
products, thus providing a
very attractive and competitive multi-mode
solution [7].
Summary
In this article, both class E and ZVS class D
amplifier topologies were evaluated for their
ability to address the demands of wireless power
transfer to the Rezence standard. A fundamental
limitation of the class E amplifier topology
is that output power and efficiency roll-off
rapidly with load variations the deviate from
the optimal design value. The characteristics of
both types of amplifiers were evaluated under
the various operating conditions. Comparing the
performance showed that the ZVS class D
is a better choice than the class E amplifier,
as it generates no even-order harmonics and
can operate over a wider impedance range. In
addition, a ZVS class D amplifier can be easily
modified to support multi-mode operation for
the three wireless power standards.
References
[1] M. A. de Rooij, Wireless Power Handbook:
A Supplement to GaN Transistors for Efficient Power
Conversion. El Segundo, CA: Power Conversion
Publications, March 2015
[2] Alliance for Wireless Power (A4WP),
http://www.rezence.com/
[3] A. Lidow, M.A de Rooij, “Performance Evaluation
of Enhancement Mode GaN Transistors in Class-D and
Class-E Wireless Power Transfer Systems,” Bodo’s
Power Systems, May 2014, pp 56-60.
[4] Efficient Conversion Power Corporation, White
Paper WP014: eGaN FETs in Wireless Power Transfer
systems. www.epc-c.com
[5] A. Lidow, “How to GaN: Stable and Efficient ZVS
Class D Wireless Energy Transfer at 6.78 MHz,”
EEWeb: Pulse Magazine, Issue 126, PP 24-31, July 2014.
[6] A. Lidow, “Wi GaN: eGaN® FETs In Wide Load Range
High Efficiency Power,” EEWeb: Wi Wireless & RF
Magazine, Nov. 2014 pp 13-17.
[7] Linear Technology, LTspice Design Simulation
and Device Models, [Online] Available:
www.linear.com/ltspice
[8] M.A de Rooij, “Topology Performance Comparison
using eGaN® FETs in 6.78 MHz Highly Resonant
Wireless Power Transfer,” DesignCon 2015, Santa Clara,
CA, 26-29 January 2015.
[9] “System Description Wireless Power Transfer,”
Vol. I: Low Power. Part 1: Interface Definition, Version
1.0.3, September 2011.
[10] Power Matters Alliance. [Online] Available:
www.powermatters.org
Figure 10: Multi-mode amplifier using eGaN FETs.
[11] A4WP Wireless Power Transfer System Baseline
System Specification (BSS), A4WP-S-0001 v1.2.1,
May 07, 2014.
Figure 10: MulA-‐mode ampliﬁer using eGaN FETs eGaN® FET is a registered trademark of
Efficient Power Conversion Corporation.
14
15
TECH REPORT
Understanding
and Mitigating
the Effect of
Soft Errors
in Semiconductor
Memory
By Reuben George, Cypress Semiconductor
T
he past few decades have
brought about unprecedented
advancements in semiconductor
technology. However, with each advance
in semiconductor technology, new
obstacles to maintaining the exponential
improvement of process technology arise.
Cosmic Rays dispersed by the atmosphere
Source CERN
Today, CMOS technology has shrunk to
such a size that extraterrestrial radiation
and chip packaging cause failures at an
increasing rate. Since these errors are
temporary, they are called soft errors. The
A SOFT-ERROR IS A
CHANGE OF STATE
first instance of soft errors was in 1978,
INDUCED BY AN
when Intel was unable to deliver its chips
ENERGETIC PARTICLE.
to AT&T due to uranium-contaminated
packaging modules. Intel, while coining the
HOWEVER, UNLIKE
term “soft fail,” reported that radioactive
A HARD ERROR, THE
contamination could cause not only flips in
AFFECTED DEVICE’S
stored data, but also microcontroller lockup. At Cypress Semiconductor, we came
NORMAL OPERATION
across the first instance of soft errors in
CAN BE RESTORED
2001, when a large telecommunications
BY A SIMPLE RESET/
client found that a single soft error in an
SRAM was causing hundreds of computers
REWRITE OPERATION.
in a system farm to crash.
16
17
TECH REPORT
THE FIRST
INSTANCE OF
SOFT ERRORS
WAS IN 1978,
WHEN INTEL
WAS UNABLE
TO DELIVER ITS
CHIPS TO
AT&T DUE TO
URANIUMCONTAMINATED
PACKAGING
MODULES.
As memory process technology scales
for improved performance and power,
the reduced voltage and shrinking node
capacitance makes these devices more
susceptible to soft errors. Soft errors
not only corrupt data, but can also lead
to loss of function and system critical
failures. Industrial controllers, military
equipment, networking systems,
medical devices, automotive electronics,
servers, handheld devices, and consumer
applications are especially vulnerable
to the adverse effects of soft errors. An
uncorrected soft error can lead to system
failures in mission critical applications
such as implantable medical devices and
automotive engine control, as well as
high-end security systems. Soft errors
have the potential to cause elevator
controllers to malfunction, while in a
networking system it can cause the
traffic to go haywire. Such occurrences,
though rare, have the potential to
cause havoc at a massive scale.
A soft-error is a change of state induced
by an energetic particle. However, unlike
a hard error, the affected device’s normal
operation can be restored by a simple
reset/rewrite operation. Soft errors
can occur in digital and analog circuits,
transmission lines, and magnetic storage.
When a high-energy particle interacts with
the semiconductor substrate, it generates
many electron-hole pairs. The resulting
electric field in the depletion region
causes a charge drift, creating current
disturbance. If the charge displacement
overcomes the critical charge stored in
the memory cell, the stored data may flip,
causing an error when it is next read. Soft
errors manifest themselves as single-bit
upsets (SBU) or multi-bit upsets (MBU),
depending on the energy of the causative
particle. An SBU occurs when only one bit
is flipped by a single energetic particle;
while an MBU occurs when a high energy
particle flips multiple bits in a word.
The rate that measures soft errors—
Soft Error Rate (SER)—determines
the probability of device failure due to
energetic particles. Since soft errors are
random, the occurrence of soft errors
doesn’t define reliability but rather
the rate of failure of the memory.
Causes of Soft Errors
ALPHA PARTICLES
Alpha particles are emitted by radioactive
nuclei in a process called alpha decay.
Alpha particles have kinetic energies of
a few MeV and are the direct cause of
soft errors in semiconductor memories.
They have a dense layer of charge and
create electron-hole pairs as they pass
through a substrate. If the disturbance is
strong enough, a bit will flip. This lasts
only for a fraction of a nanosecond,
and hence is very hard to detect.
Low-energy alpha particles are generated
by the radioactive decay of trace amounts
of Uranium-238, and Thorium-232
present in mold compounds, packages,
and other assembly materials. However
it’s nearly impossible to maintain the
ideal material purity (less than 0.001
counts per hour per cm2) needed for
reliable performance of most circuits.
Small amounts of epoxy can reduce
the incidence of soft errors by shielding
the chip from alpha radiation.
COSMIC RAYS
Manufacturers have managed to control
contaminants emitting alpha particles,
but they have been unable to counter
cosmic radiation. In fact, cosmic rays
are the likeliest cause of soft errors
in modern semiconductors, since
radioactive contaminants have been
largely controlled. The primary particles
of the cosmic rays don’t usually reach
the earth’s surface. However, they do
create a stream of energetic secondary
particles, mostly energetic neutrons.
While neutrons are uncharged and
hence can’t cause soft errors, they can
be captured by the nucleus in a chip, an
event that can result in alpha particles.
Cosmic radiation increases with altitude
due to a lower shielding effect of the
atmosphere. In addition, modules used
at the Poles are also highly susceptible
to soft errors for the same reason. To
reduce soft errors, modules used in high
exposure applications undergo a special
process called Radiation Hardening.
THERMAL NEUTRONS
Neutrons void of kinetic energy are
an important source of soft errors
due to neutron capture reactions. The
capture of a thermal neutron by a Boron
isotope (10B) nucleus, found in large
quantities in Boronphsophosilicate
glass dielectric layers, emits an alpha
particle, Lithium nucleus, and gamma
ray. Either the Alpha particle or the
Lithium nucleus can cause a soft error.
Thermal neutrons are especially
important for medical electronics
used in cancer radiation therapy. The
neutrons combined with the photon
beam used in treatment result in a
thermal neutron flux that generates a
very high rate of soft errors. However,
thermal neutrons aren’t a major
cause of soft errors nowadays, since
manufacturers eliminated borated
dielectrics by the 150nm process node.
Effect of radiation inside a MOS transistor
18
19
TECH REPORT
Mitigating Soft Errors
Soft errors can be avoided by improving
process technology and memory cell
layout, system-level changes, and
changing chip design and architecture.
Improving in Process Technology
and Memory Cell Layout
The reliability of a memory device can be
enhanced by increasing the critical charge
stored in the memory cell. The resistance
of a device to soft errors can also be
increased by using a process technology
that reduces the thickness of diffusion.
This reduces the amount of time a charge
particle spends in a memory cell. A
triple-well architecture can also be used
to drift charges away from the active
region. This process creates an opposite
electric field with respect to the NMOSdepletion region and forces charges
into the substrate. It only acts when a
soft error occurs in the NMOS region.
System-level Mitigation
At the system-level, designers can
prevent the effect of soft errors by using
external error correction code (ECC)
logic. In this technique, the user employs
additional memory chips with parity bits
for error detection and correction by.
As expected, system-level mitigation is
expensive and also adds more complexity
to the system and its software.
Changes in Chip Design
and Architecture
This is the best way to combat soft
errors. Chip designers can mitigate soft
errors by using Error Correction Code
(ECC). During a write operation, the ECC
encoder algorithm includes parity bits
with every addressable word of data
stored in the memory. During a read
operation, the ECC detection algorithm
uses parity bits to determine whether any
of the data bits have changed. If there
is single-bit error, the ECC correction
algorithm determines the location of
the concerned bit. It can then facilitate
error correction by flipping the data
bit back to its complementary value.
ECC alone, however, cannot address
multi-bit upsets (MBU). For these,
COSMIC RAYS ARE THE LIKELIEST CAUSE OF SOFT ERRORS
IN MODERN SEMICONDUCTORS, SINCE RADIOACTIVE
CONTAMINANTS HAVE BEEN LARGELY CONTROLLED.
designers have to implement bit
interleaving. This technique arranges bit
lines such that physically adjacent bits
are mapped to different word registers.
The bit-interleave distance separates
two consecutive bits mapped to the
same word register. If the bit-interleave
distance is greater than the spread of
a multi-cell hit, it results in single bit
upset (SBUs) in multiple words rather
than a multi-bit upset (MBU) in a single
word. Typical bit-interleave distance
depends on the process technology.
Neutron testing is performed with a
subsequent physical MBU analysis to
determine the safe interleaving distance
for each process technology node. In a
bit-interleaved memory, single-bit error
correction algorithm can be used to
detect and correct all errors. The ECC
algorithm applies only to the copy of
the affected word of data. The data as
it resides in memory still contains the
flipped bit. If this flipped bit in memory
remains uncorrected, exposure to
another bit flipping in the same word
of data can result in a multi-bit upset.
It is important, therefore, that the ECC
logic indicates the occurrence and
correction of a single-bit upset. The
system can then use this information
to recognize the event and writeback corrected data. This technique
is known as memory scrubbing.
With semiconductor chips being
manufactured on shrinking process
nodes, the risk of soft errors is
increasing. Hence, many experts
expect soft errors to be a limiting
factor to continued shrinking unless
new technology is developed that
overcomes soft errors. Furthermore,
with technology entering more spheres
of human life, the need for reliability is
bound to increase. This trend increases
the need for on-chip Error Correcting
Code (ECC) for memory modules. All
major memory manufacturers have
started releasing chips with on-chip ECC
to meet the demand for high reliability
memories. Given the high-performance
applications that SRAM devices are
used for, error correcting capabilities are
a must for SRAMs. Cypress, the world
leader in SRAMs, has a family of ultrareliable Asynchronous SRAMs with
on-chip ECC and bit interleaving.
SOFT ERRORS CAN OCCUR IN DIGITAL AND ANALOG CIRCUITS,
TRANSMISSION LINES, AND MAGNETIC STORAGE.
20
21
Entry Phase
Submission Phase
Completion Phase
Winners Announced
January 1
March 1
April 15
August 1
GRAND PRIZE
NXP Logic Presents
Clemens Valens
The
Big
I.D.E.A.
2015 International Design Engineering Award
J
oin NXP and Mouser in the 2015 Big I.D.E.A.,
JANUARY 1 - ENTRY PHASE
» Fill in and submit questionnaire. (Special bonus drawing for entries
before March 15. Five contestants will win prizes worth $100 each.)
» Advance to the Submission Phase.
Click here to register and start the contest!
http://convergencepromotions.com/TheBigIdea.html
MARCH 1 - SUBMISSION PHASE
» Contestants will produce a schematic using NXP’s products.
(Special bonus drawing for schematics before April 15. Ten contestants
win prizes worth $200 each.)
» Selected contestants will advance to the Completion Phase.
Click here to view the Submission Phase rules and instructions.
https://www.youtube.com/watch?x-yt-ts=1421782837&x-yt-cl=84359240&v=LlJOa-QR45I
APRIL 15 - COMPLETION PHASE
» Design kits will be sent to contestants selected from the Submission Phase.
» Entries must be submitted for judging by June 30.
a design contest featuring NXP’s unique
AUGUST 1 - WINNERS ANNOUNCED
product line-up across the spectrum,
» GRAND PRIZE: $3000 Prize Value
including Dual Configurable Logic, Smart Analog,
» FIRST PLACE: $2000 Prize Value
MOSFETs, and Power.
» SECOND PLACE: $1500 Prize Value
Everyone has a chance to win thousands of
dollars worth of prizes, with awards at every
» THIRD PLACE: $1000 Prize Value
» HONORABLE MENTION: $500 Prize Value
level of the competition.
22
23
COVER STORY
New RUGGED
Industrial-Grade
TRANSFORMS the
Maker Movement
By Glenn ImObersteg
Convergence Promotions
24
The Raspberry Pi™, Banana Pi, Beagle Board, and Panda Board
have opened up a wealth of new resources for students and
DIY-ers interested in electronic design. Bridging the gap
between products built for hobby applications and those used
in mainstream, industrial, or commercial products has been
daunting—until now. This article introduces a new generation
of single-board computer (SBC) that has been designed for
engineers searching for the simplicity and programmability of a
Raspberry Pi and Beagle Board in a production-ready, industrialgrade SBC called the Boxer Board.
25
COVER STORY
The Life of Pi
Raspberry Pi was conceived in 2006 by
Raspberry Pi Foundation Trustee, Eben
Upton, and an assemblage of teachers,
academics, and computer enthusiasts
with the intent of devising a simple
computer to inspire students. The 2012
product launch was met with instant
acclaim and success; one distributor,
Premier Farnell, sold out within a few
minutes, and another, RS Components,
took over 100,000 pre-orders on day one.
Send in the Clones
The instant success of Raspberry Pi
quickly spawned a number of clones,
including the Banana Pi, Arduino™,
Beagle Board, Panda Board, and the
rest of the animal kingdom and new
food groups. All of these new boards
were similar in their low-cost platform
designs and they all targeted the
student, DIY, and hobby markets.
Trying on Capes and Hats
One of the reasons for the popularity
of the Raspberry Pi and Beagle Board
has always been the ability to attach
physical, application-specific hardware
to the GPIO (General Purpose Input/
Output) connector. An entire cottage
industry spawned from supporting
hundreds of boards and add-ons,
including buttons, LCDs, LEDs, sensors,
and more. Recently, the fashionable
HATs (Hardware Attached on Top) joined
the family, even amidst the controversy
that many developers claim the idea is
borrowed from BeagleBone capes.
DIY and Student Modules:
Not Ready for Prime Time
Sales of Raspberry Pi are edging towards
the five million mark, and the lure of lowcost boards, easy programmability, and
a plethora of accessories is undeniable.
The popularity of these modules makes
a convincing argument for developing
‘real-life’ projects using one of the boards
discussed here, if you can overcome
the dichotomy between student
applications and real-world applications
in the industrial, medical and aerospace
industries. There are three primary
reasons why the hobby modules will not
be able to successfully make that leap:
Sustainability and Continuity of Supply
Will today’s hobby boards be available in
quantity in five or ten years when you need
to do a product update? The chances are
that you won’t be making those decisions.
If you are a typical engineer, you will
have changed jobs 2.5 times (Google’s
average for engineering job life-span),
and if you have used a Raspberry Pi 1
or 2, or B, or B+ in an OEM application,
what obstacles—such as inventory and
technical support—will your successors
have to contend with in a redesign? The
solution is clear: for a product to be a valid
solution in the embedded market, it needs
to have continuity of supply, component
control, and obsolescence management.
For a product to be a valid solution in the embedded market, it needs to have
continuity of supply, component control, and obsolescence management.
26
Engineering Support
The professional engineering community
will never be able to replicate the depth
of enthusiasm that the foundations
and communities offer their colleagues
in design and applications support,
products, and hardware and software
fixes. However, this enthusiasm can’t
replace the 24-hour manufacturer
hotlines and field application engineers
that many manufacturers employ to
provide customer support worldwide.
Certification and Quality Control
Engineers designing applications
from IoT to avionics have to meet
the strictest standards, such as
quality (ISO 9001) or environmental
management (EN ISO 14001) standards,
in addition to certification for every
industry the product will be used.
Crossing the Great Divide
How can you decide between the
functionality, programmability, easy
accessibility to peripherals, and low cost
of the DIY modules versus a productionready, industrial-grade reliable product?
Now you can, and we have discovered
it is possible to have your pie and eat
it too. TQ-Group has designed a board
with the TI Sitara™ AM3352 that is
simple to program, flexible, affordable,
and manufactured to the strictest
environmental and quality management
standards. Certified for medical, aviation,
automotive, and other OEM applications,
and backed by a team of FAEs in Europe
and North America, this board is rugged,
industrial-grade, and productionready. We call it the Boxer Board.
THE IMPORTANCE
OF SUSTAINABILITY:
A Tale of Three CPUs
Consider the following adages:
• Design cycles are measured in years
• Engineers get really attached to their devices
• MCUs take on a life of their own long after
they’re designed into applications
The following conversation (or urban myth?)
from a few years ago is a classic illustration of
the importance of continuity of supply; a Boeing
engineer in the late 1990’s remarked that a
Boeing 777 aircraft had three redundant flight
computers, each fitted with Intel 486, Motorola
68K, and AMD 29K processors, and each set up
in a voting scheme to compensate for hardware
and software errors. Although there was a debate
about whether the third CPU was an Intel i960 or
i860, the fact is—all of these chips had been out
of production for more than a decade. They had
firewalled software teams to develop separate
code bases for each CPU so that application level
bugs would not be replicated across all three
architectures, which feed into the voting system.
With this level of complexity, there was no way
that this system was going to be re-designed for
quite some time. The moral of this tale is that for
a product to be a valid solution in the embedded
market, it needs continuity of supply, component
control and obsolescence management.
27
COVER STORY
The new Boxer Board SBC from
TQ combines the simplicity of the
BeagleBone Black with a rugged design
for industrial applications.
The new Boxer Board (TQ SBCa335x)
was designed from specifications and
requirements for a customer who
manufactures water treatment plants
for emerging nations. The requirements
for the development were:
• Ease of programming and low-cost
• Industry certifications for
in-plant operations
• Guarantee of long-term availability
• Continuous and reliable operation
at high temperatures
Dominik Mücke
and Jens Linke
from
TQ-Systems GmbH
As a solution, engineers Dominik Mücke
and Jens Linke from TQ-Systems GmbH
in Munich, Germany, developed the
SBCa335x—an SBC using the same
processor family as the BeagleBone
Black with pin-compatible headers
for the BeagleBone Black Capes and
Raspberry Pi B+ Capes and Hats.
Nick-named the ‘Boxer Board’ by
Convergence Promotions LLC, the North
American sales and distribution company
for TQ-Group, the SBCa335x debuted
at Embedded World in late February
2015 and received instant acclaim.
The Boxer Board is based on the Sitara™
AM3352 (optional 3354) processor
(800 MHz ARM Cortex™-A8 Core) from
Texas Instruments. Its compact and
rugged design of only 4.8” (12 cm) by
3.2” (8 cm), temperature range of -20°C
to +70°C, and low-power consumption
(typ. 2W), makes the Boxer Board
suitable for industrial applications in
the smallest of spaces. It provides pincompatibility with the Raspberry Pi B+,
so adding capes and hats is a breeze.
Interfaces for Even the Most
Demanding Applications
Even with WiFi, Bluetooth, and a number of other interfaces
not included with Raspberry Pi or BeagleBone Black,
the production-ready, industrial-grade Boxer Board with
the Sitara™ AM3352 will still retail for under $100.
Boxer Board Specification
Microprocessor
• 2x Gigabit Ethernet, 2x
USB (Host and OTG)
• CAN and WiFi (2.4 GHz b/g/n)
and Bluetooth 4.0
AM3352, AM3354 (on request)
256MB DDR3L-SDRAM, 512KB on request
Memory
16MB NOR-Flash, Up to 16MB on request
1x Micro-SD-Card
1x CAN (3.3V, not galvanically separated) ISO 11898
2x 10/100/1000 Mbit (LS switch) IEEE 1588
1x I²C
System
Interfaces
1x SPI
1x UART (UART to TTL Serial Cable 3.3V)
2x USB 1x 2.0 OTG (Micro USB), 1x
USB 2.0 HOST (USB Typ A)
1x WiFi – 2.4 GHz IEEE Std 802.11 b/g/n
The Boxer Board has an
impressive number and variety
of interfaces including:
1x Bluetooth 4.0
6x 12-bit ADC channels (1.8V MAX)
Other Interfaces
& Busses
20x GPIO
16-bit data bus width
CPU JTAG debugging interface
General
Dimensions
120 mm x 80 mm
• 1x HDMI, micro SD and access
to UART, SPI, I2C, 20 GPIOs
Audio
1x Audio (Headphone, Mic In, Line In, Line Out)
RTC
Yes
• 6x 12-bit ADC channels, and more
Reset Button
Yes
Temperature
Sensor
Yes, with 2KByte EEPROM
System
Connector
Pinstrip (80 pins), including Raspberry
Pi B+ compatible pinstrip
Temperature
Range
-20°C…+70°C
Operating
Systems
Linux 3.14, QNX, WEC 2013
This array of interfaces makes the Boxer
Board applicable for a wide range of
industrial and medical applications
particularly for the IoT and M2M markets.
Its compatible interface to Raspberry
Pi B+ Capes and Hats provides added
flexibility and speeds time-to-market.
28
Priced under $100 with WiFi and Bluetooth
WHAT’S IN A NAME?
Raspberry Pi:
“A reference to a fruit naming
tradition in the old days of
microcomputers. A lot of computer
companies were named after
fruit. There’s Tangerine Computer
Systems, Apricot Computers, and
the old British company Acorn,
which is a family of fruit. The
name Pi came about because
originally they were going to
produce a computer that could
only really run Python. So the
Pi in there is for Python”.*
Beagle Board:
Named for “Boris” the Beagle
Boxer Board:
Named for the author’s dog
“Winston,” an 85-pound Boxer.
*Techspot interview with Eben Upton,
by Jose Vilches on May 22, 2012
29
COVER STORY
Block Diagram SBCa335x
BEAGLEBONE BLACK
700 MHz ARM1176JZFS
800 MHz TI Sitara AM3352
ARM Cortex-A8
512MB DDR3L
512MB SDRAM
256MB DDR3L, Optional
512MB/1GB
2GB on-board
eMMC, Micro SD
SD
16MB NOR Flash, Micro SD
1x USB Host, 1x MiniUSB Client, 1x 10/100
Mbps Ethernet
2x USB Hosts, 1x MicroUSB Power, 1x 10/100
Mbps Ethernet, RPi
camera connector
2x Ethernet 10/100/1000, 2x
USB (Host & OTG), 1x CAN,
1x SPI, 1x I2C, 6x 12-bit ADC
WiFi/Bluetooth
No
No
2.4GHz 802.11 b/g/n
and Bluetooth 4.0
GPIO Capability
65 Pins
8 Pins
20 pins
No
No
CPU JTAG debug connector
Operating Systems
Angstrom (Default), Ubuntu,
Android, ArchLinux, Gentoo,
Minix, RISC OS, others…
Raspbian (Recommended),
Ubuntu, Android,
ArchLinux, FreeBSD,
Fedora, RISC OS, others…
Linux 3.14, QNX & WEC2013
Video Connections
1x Micro-HDMI
1x HDMI, 1x Composite
1x mini HDMI
1280×1024 (5:4), 1024×768
(4:3), 1280×720 (16:9),
1440×900 (16:10): all at 16-bit
Extensive from 640×350
up to 1920×1200, this
includes 1080p
WXGA 1366x768
Stereo over HDMI
Stereo over HDMI, Stereo
from 3.5mm jack
Stereo over HDMI, Stereo
from 3.5mm jack
210-460mA @ 5V under
varying conditions
150-350mA @ 5V under
varying conditions
3x AA/AAA, 5V Micro
USB. 750mA @ 5V under
varying conditions (WiFi
and Bluetooth)
0°C to +70°C
temperature range
Untested -25°C to +80°C
temperature range
Rugged construction for
industrial use and -20°C to
+70°C temperature range
No
No
ISO 9001, EN 9100
(Aviation), ISO 13485
(Medical technology), ISO
16949 (automotive)
Size
3.4x2.1 inches
3.4x2.2 inches
4.8x3.2 inches
Price
$50
$35
Sub- $100*
*Price subject to change
RAM
Storage
Peripherals
JTAG
The Boxer Board runs on Linux, QNX
and WEC 2013, (with VXWorks available
on request) and can be ordered in two
memory versions (256 MB DDR3L
SDRAM and 512 MB DDR3L SDRAM).
Certification for Your Applications and
Continuity of Supply Until 2025
As with all of the TQ products, quality
management is of major importance
(TQ stands for ‘Technology in Quality’).
TQ-Group is certified in accordance with
ISO 9001 (Quality Management), ISO
14001 (Environmental Management),
EN 9100 (Civil Aviation), ISO 13485
and MDD (Medical Technology), as
well as ISO/TS 16949 (Automotive).
30
Summary
The legacy of Raspberry Pi and other
hobby-level modules will be that it
revolutionized the board industry by
making low-cost and easy-to-design
modules and feature-rich accessories
available to millions worldwide. The
Boxer Board is the next step in the
evolution of these boards from hobbylevel to industrial-grade solutions
for the thousands of embedded
engineers who started as students
on the hobby platforms and have
graduated to developing embedded
applications for IoT, industrial, medical,
automotive and other industries.
The Boxer Board will be available
in May 2015 from TQ-Systems
(www.TQ-Group.com)
www.TQ-Group.com in EMEA and
from Convergence Promotions
(www.embeddedmodules.net)
www.embeddedmodules.net in
North America.
TQ BOXER BOARD
1GHz TI Sitara AM3359
ARM Cortex-A8
Processor
BSPs and Operating Systems
You Can Work With
RASPBERRY PI
Supported Resolutions
Audio
Power Draw
Environmental
Certification
31
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