Brett Fox - EEWeb

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Brett Fox 

Touchstone 

Semiconductor, Inc. 

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Issue 24 

December 6, 2011 

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TABLE OF CONTENTS 

Brett Fox 4 

Touchstone Semiconductor, Inc. 

Interview with Brett Fox - President and CEO 

Featured Products 

Software and Hardware Platform Enable 10 

Over One TeraFlop Processing Rates 

BY MICHAEL PARKER WITH ALTERA 

An introduction to a processing platform that provides the advantages of both floating point and 

fixed point processing. 

System Perspective on Specifying 14 

Electronic Power Supplies:Load 

Characterization 

BY BOB STOWE WITH TRUE POWER RESEARCH 

Learn about the effect of the load when specifying a power supply. 

RTZ - Return to Zero Comic 17 

EEWeb | Electrical Engineering Community Visit www.eeweb.com 3 

8 

TABLE OF CONTENTS

INTERVIEW 

Brett Fox 

Touchstone Semiconductor, Inc. 

How did Touchstone come 

about? 

The idea for this company has been 

floating around with me for many 

years, actually since I left Maxim in 

early 2000. Back then was not the 

right time to start a company like 

Touchstone. At the time, the funding 

was going toward businesses that 

were one-product, one-customer 

type models. VCs could make an 

investment and it could quickly turn 

into money. We were trying to build 

a real company. When I left Micrel 

in 2005 I started to think about what 

I wanted to do. I was fortunate 

enough to know some people in 

venture capital. Crosslink Capital, a 

VC firm in San Francisco, asked me 

to be an Entrepreneur in Residence 

(EIR), which is a pretty cool job. 

You essentially are given a salary, 

an office, and a business card. You 

get to sit in on their meetings and 

see the inner workings of how a 

venture capital firm works. They 

will help you look at companies in 

your space, and if you want to start 

Brett Fox - President and CEO at Touchstone Semiconductor, Inc. 

a company, they will help you do 

that. The real genesis of Touchstone 

started there. I started to work on 

finding a team of people, flushing 

out the business plan more, making 

contacts and all those types of 

things. When I left Crosslink in early 

2008, Touchstone was formed, and 

I started raising money in earnest. 

What was the most 

challenging aspect of starting 

Touchstone? 

The most challenging thing was 

raising the money. It took us two 

years to raise our funding. We 

started in early 2008 and found the 

first investor, Opus Capital, within 

a month. Most people say if you 

can find one investor, you will find 

another one easily. In our particular 

case, because of the economic 

environment of 2008 combined with 

the environment of semiconductor 

investments (which continued to 

worsen throughout the year), we 

saw that it was unlikely we would 

close our funding in 2008. After 

2008, we really had to regroup. 

Opus stood with us. In the summer 

of 2009, the economic environment 

was getting better; VCs were 

starting to put money to work. We 


FEATURED INTERVIEW

INTERVIEW 

started to raise money in earnest 

again. In early fall, we found Khosla 

Ventures as our second investor. I 

am thrilled at how it worked out; we 

found two really good investors who 

know our space. Opus’ Managing 

Partner, Gill Cogan, was actually 

an original investor in Maxim, and 

when you look at our business 

model, we knew he would be a 

fantastic resource. Pierre Lamond 

led the deal for Khosla Ventures. 

Pierre is a co-founder of National 

Semiconductor and was involved 

with Linear Technology and many 

other successful semiconductor 

companies. He was very familiar 

with what we were doing, and was 

looking for a company like ours to 

invest in. Our funding (money in 

the bank) came on March 8, 2010, 

and since that time it has been a 

relatively straightforward ride for 

the company. I am not saying there 

have not been bumps along the way, 

because indeed there are always 

unforeseen things. 

Can you tell us about the 

Founders of Touchstone 

Semiconductor, Inc.? 

All of us either come from Maxim, 

Linear, or Analog Devices. Most of 

the team has worked together in 

one way, shape, or form. 

I have my BSEE from the University 

of California, San Diego, and 

my MBA from the University of 

Southern California. In 1989 I joined 

Maxim, and before that I was a 

designer for about five years. When 

I joined Maxim, it was a roughly 

$40 million company, and when I 

left in 2000, they were making over 

a billion dollars in revenue. I was 

very fortunate—right place, right 

time, and right set of skills. I ended 

up setting the strategic direction 

for most areas of the company. 

After Maxim I worked at a start-up 

for about nine months. Then I went 

to Micrel for about four years and 

ran the high bandwidth division. I 

ended up turning that around from 

being the least profitable division of 

the company to the most profitable 

when I left. From there I went to 

Crosslink Capital for about a year, 

and then started working full time 

on Touchstone. 

The thing that we really 

want customers to think 

about Touchstone is that 

the company is doing 

cool and unique things. 

Hopefully, as time goes 

on, we will achieve 

that reputation, and 

customers will look to 

us for those types of cool 

and unique products. 

Jeroen Fonderie, the Vice President 

of Engineering, has a PhD from Delft 

University in the Netherlands. That is 

one of the best engineering schools 

for analog designers in Europe. 

When he was there he wrote a book 

on op amp design. He has written 

over 20 scientific publications, and 

he holds seven patents. Beyond 

that, he is a fantastic manager, and 

a very good business man. In the 

Analog world, that is a very rare 

combination. When you put all three 

of those factors together, you have 

a great VP of Engineering for a 

company like Touchstone. 

Adolfo Garcia, our VP of Marketing 

and Applications, started out also as 

a designer. He went from being in 

the design world to joining Analog 

Devices, and worked there for 

several years before moving on to 

Linear Technology and continuing in 

applications for several more years. 

He then worked at Micrel, which is 

where we crossed paths. He was 

running part of that business on the 

analog side. He then worked at a 

couple of other analog companies, 

and when I was looking to start 

Touchstone, he was the ideal guy to 

run marketing and applications. You 

want someone who is technically 

very strong and who can cover a lot 

of different products. 

The design team is mostly from 

Maxim, Linear, Analog Devices, 

National, or MPS. All of the designers 

in the company have also worked 

together in some way, shape, or 

form. Some of the designers and I 

go back 20 years; they all average 

about 20 years of experience and 

about 10 patents per designer. So 

this is a group that can hit the ground 

running, can work independently, 

and will be able to get things done 

in a reasonable time period. We 

also wanted people that fit in our 

company culture, you want people 

that work well together. It does not 

mean that everyone has to be best 

friends or see eye to eye on every 

issue, but they have to be able to 

work well together and understand 


FEATURED INTERVIEW

INTERVIEW 

the focus of the company. Everyone 

here believes in our model and is 

moving forward to implement our 

strategy. 

How do you choose the 

products to manufacture? 

We have two strategies we are 

working in parallel. The primary 

focus at the beginning was 

alternative source products. We 

did this because it solves a big 

problem that our customers face 

today. Most of the parts in the High 

Performance Analog segment are 

sole-sourced. That means that there 

is one source, and if customers have 

a problem obtaining a product from 

the primary source, they are out 

of luck. We provide an alternative 

source, and an assurance of supply 

they cannot have using only Maxim. 

In parallel with that, we are working 

on proprietary parts, which is the 

long-term future of the company. 

We want customers to think of us as 

a very different company. We want 

to develop things that are really 

different, unique, and cool to solve 

problems that are not being solved 

today. That is our basic product 

choosing methodology. 

Our philosophy follows the words 

of Hall of Fame baseball player 

Willie Keeler: “Hit ‘em where they 

ain’t.” To us, this means don’t create 

the obvious products because 

customers will naturally gravitate 

toward the big companies. We are 

pursuing a niche strategy where 

we focus on markets that are big 

enough for us to make money but 

not so big that the larger companies 

would be interested in pursuing 

them. 

What industry sectors are you 

looking at? 

We are pretty flexible in terms of 

what we do. The initial focus of the 

company is toward industrial types 

of companies. We have naturally 

evolved to low power applications. 

We are combining those two things 

together and it seems to be working. 

As you target single-source 

applications components, is 

there any concern with IP as 

you design this part? 

We are designing in a different 

technology from the primary source, 

so almost by definition we have to 

use different architectures. We look 

at patents before we start. We do not 

want to infringe on someone else’s 

patents. We do not want to cause 

any unneeded issues. 

We want to fill niches 

in the marketplace, 

build our business up, 

and show engineers 

that we can solve 

problems that have not 

been solved before. 

Can you tell us more about 

the manufacturing and 

testing? 

We are using TSMC as our primary 

foundry. They are a great partner 

and have been very supportive 

along the way. We do most of 

our development in their 0.18µ 

technology but we are not limited to 

just that. We can use any technology 

that they have. That is the nice thing 

about our business model; we are 

flexible. We are able to pick the 

right technology for the product. 

We are old school with regard to 

testing. We test everything that we 

develop. If we are guaranteeing our 

specifications over temperature, 

we test and make sure that it will 

perform exactly what we say it will. 

How do you keep up with 

inventory? 

That is one of the big advantages 

for us. Because everything we are 

developing is on 8-inch wafers and 

we hold a lot of stuff in die banks, it 

does not cost us a huge amount of 

money to manufacture. If someone 

comes in with a huge order, we are 

able to manufacture, test, and ship 

it pretty fast. 

Can you tell us about your low 

power op amp? 

Customers seem to love the 

TS1001 600nA, 0.8V Op Amp. Even 

customers who cannot use it seem 

to love it, which is really nice for us. 

It has been a great door opener for 

the company. Where we are seeing 

a lot of use for this part is in lowpower 

applications. If someone 

needs bandwidth less than a 

kilohertz, and you want to reduce 

power consumption, it is perfect. 

Customers are getting really excited 

about it in those specific types of 

applications. 

What can we expect to see 

from Touchstone in the future? 

We have a couple of different 


FEATURED INTERVIEW

INTERVIEW 

product families coming out at the 

end of September and October 

2011. I am a little bit hesitant to 

say anything until they come out 

because the scary thing in our 

business is until you see it and know 

it works, it’s not a sure thing. 

The thing that we really want 

customers to think about Touchstone 

is that the company is doing cool 

and unique things. Hopefully, as 

time goes on we will achieve that 

reputation, and customers will look 

to us for those types of cool and 

unique products. We want to fill 

niches in the marketplace, build our 

business up, and show engineers 

that we can solve problems that 

have not been solved before. 

How many products would 

you like to see Touchstone 

having in five years? 

Our minimum goal is 200, and it 

looks like we will easily be able 

to achieve that. We will continue 




1.800.574.2791 



expanding our support staff around 

those products. Right now we have 

25 people in the company, and 

we are always looking for good 

designers. We have a very high bar 

regarding who we hire. We have an 

extremely talented and cohesive 

team, so it is an elite group that 

people will be joining. ■ 


FEATURED INTERVIEW

FEATURED PRODUCTS 

Fastest 14-bit Sample-and-Hold Amplifier 

Datel, a business unit of Murata Power Solutions has announced what it 

claims is the world’s fastest stand alone 14bit sample and hold amplifier. 

According to the company, the SHM-14 amplifier has a 70MHz full power 

bandwidth and 250MHz small signal bandwidth that achieves 12 and 

14bit acquisitions within 25ns (/-0.012%) and 35ns (/-0.003%) respectively. 

Datel adds that the low power device has an aperture jitter within 1ps 

and a low output noise of 65uV rms. Output linearity is within +/-0.0023%, 

while digital sample/hold inputs are differential and compatible with all 

logic families including TTL, CMOS and ECL. For more information, 

please click here. 

3-GHz, 10-Output Level Translator 

The LMK00301 is a 3-GHz, 10-output differential fanout buffer intended 

for high-frequency, low-jitter clock/data distribution and level translation. 

The input clock can be selected from two differential inputs or one 

crystal input. The selected input clock is distributed to two banks of 5 

differential outputs and one LVCMOS output. Each output bank can be 

configured as LVPECL, LVDS, or HCSL drivers, or disabled to reduce 

power. The LVCMOS output has a synchronous enable input for runtpulse-free 

operation when enabled or disabled. The LMK00301 can 

be powered from a single 3.3 V supply, or dual 3.3 V/2.5 V supplies for 

lower power operation. The LMK00301 provides high performance, 

versatility, and power efficiency, making it ideal for replacing fixedoutput 

buffer devices while increasing timing margin in the system. For 

more information, please click here. 

Tightest Offset Current-Sense Amplifiers 

Touchstone Semiconductor, a developer of high-performance analog 

integrated circuit solutions, announced the TS1100 family of 1µA currentsense 

amplifiers that cut offset to 30µV, over 3X tighter than the closest 

competitor. The tight offset allows users to not have to increase power 

consumption in order to achieve improved accuracy. This is something 

that cannot be done with any other low power current sense amplifier. 

The TS1100 is available in four gain options from 25V/V to 200V/V, so 

customers can choose the ideal gain option for their unique application. 

For more information, please click here. 


FEATURED PRODUCTS

Avago Technologies Motion Control Solutions 

World’s Smallest Miniature 

Reflective 3-channel Encoder 

Features Advantages Benefits 

3-channel encoding 

(AB and I) 

Index Signal “I” No need for separate 

components to generate 

the index signal 

Miniature size Surface mount leadless 

package: 3.95 mm (L) x 

3.4mm (W) x 0.95mm H) 

Ability to fit into 

miniature motor designs 

304 LPI High encoding resolution Various CPR capable 

by adjusting to the 

matching ROP of the 

codewheel 

Built in Interpolator of 

1x, 2x, and 4x 

High operating 

frequencies: 55 kHz 

at 1x interpolation 

1x, 2x and 4x via external 

pinouts 

Operating frequencies can 

be increased by external 

interpolator pinouts by 

maximum of 4x 

Index gating Options available for both 

gated and ungated versions 

-20°C to 85°C Industrial application 

capable 

Base CPR resolution can 

be interpolated by end 

user 

Corresponding high 

RPM performance with 

increased frequencies 

Catering for various user 

gating requirements 

Covering consumer, 

commercial and 

industrial applications 

Avago Technologies AEDR-850x three 

channel reflective encoders integrate 

an LED light source, photo detector 

and interpolator circuitry. 

It is best suited to applications where 

small size and space matters! 

Applications include medical hand 

held devices, camera phones, wheel 

chairs, actuator, vending machine 

applications, just to name a few. 

To request a free sample go to: 

www.avagotech.com/motioncontrol

1Processing Rates 

Software and Hardware 

Platforms Enable Over 

TERAFLOP 

Computing applications have long used floating 

point numerical processing, including many in CPU 

architectures, which are mathematically superior 

and support wide dynamic ranges. However, most 

embedded applications have traditionally used fixed 

point processing. Despite significantly increasing 

development complexity (often three times the time of 

floating point development), fixed point microprocessors, 

DSPs, and FPGAs can generally provide lower power 

consumption, lower costs, and in the case of FPGAs, 

much higher processing rates. 

A new FPGA-based floating point flow is available that 

allows for the same high processing rate as enjoyed 

by fixed point applications to be achieved in floating 

point applications. A floating point co-processor which 

can be tightly coupled to FPGA hardware is also newly 

available, allowing both hardware and software floating 

point data processing to be leveraged. In addition, both 

of these new capabilities still support high throughput, 

fixed point processing for the parts of the DSP datapath 

that do not need the dynamic range of floating point 

processing. The result is a processing platform that 

Michael Parker 

Sr Technical Manager 

provides the advantages of both floating point and 

fixed point processing, while providing the flexibility to 

seamlessly partition and optimize the implementation 

between hardware and software. 

Parallelism is a key advantage of a hardware solution 

like FPGAs, but it is often not applied to floating point 

signal processing because long latencies make the 

data dependencies in algorithms, such as matrix 

decomposition, difficult to manage. Therefore, the 

resultant systems offered poor performance levels and 

were uncompetitive with other platforms such as GPU or 

multi-core CPU architectures. 

Altera has developed a floating point design flow 

that overcomes these issues. Rather than building a 

datapath from individual operators, the entire datapath 

is considered as a single function, with inter-operator 

redundancy factored out. Mantissa representation can 

be converted to hardware-friendly twos complement, 

and mantissa widths extended to reduce the frequency 

of normalizations. Elementary functions can be 

implemented as much as possible using hard multipliers, 

EEWeb | Electrical Engineering Community Visit www.eeweb.com 10

TECHNICAL ARTICLE 

which offer guaranteed internal routing and timing, as 

well as low power and latency. New techniques can be 

applied for matrix decompositions, with the algorithms 

restructured to remove most of the data dependencies, 

so that parallel—and therefore high latency—datapaths 

can be used for these computations. 

This approach is known as “Fused Datapath,” and when 

combined with a new 28nm Variable Precision DSP 

block architecture, offers extremely high data processing 

capabilities, in excess of one TeraFLOPS on a single 

FPGA die. The Fused Datapath technology has been 

embedded in Altera’s DSPBuilder design suite, which 

allows the full simulation and system design capabilities 

of Mathworks’ Matlab and Simulink to be utilized. This 

FPGA innovation in high-performance floating point 

enables the parallel hardware architecture advantages 

to be used in the very highest performance applications 

where the dynamic range of floating point is required. 

An example of the matrix inversion processing capability 

with the latest floating point Cholesky matrix processing 

design is shown in Figure 1. 

Multi-Channel Cholesky Inversion Core 

Matrix Size Vector Size Throughput (matrices/sec) Latency (us) 

100x100 

50x50 

75x75 

50x50 

25x25 

20x20 

50 

50 

25 

25 

25 

20 

29,900 

128,000 

42,700 

118,000 

256,000 

1,000,000 

380 

270 

392 

304 

71 

96 

Multiple single precision Cholesky cores may be implemented with a single FPGA 

Figure 1: FPGA-based Floating Point Processing Throughput 

Example 

For more information on Altera’s FPGA floating point 

design flow using Altera’s DSPBuilder Advanced 

Blockset and Mathworks’ Simulink, please refer to the 

recent BDTI whitepaper and toolflow evaluation available 

here. 

Most floating point applications are currently 

implemented in software. With this new FPGA design 

flow now offering extremely high processing rates, a 

new architecture can be conceived that uses a tightly 

coupled C-programmable engine as a co-processor to 

the FPGA, rather than just the reverse. The FPGA can 

implement the repetitive, high GFLOPS portions of the 

algorithm, while the co-processor can deal with the 

more complicated and data-dependent algorithms. This 

approach would combine the performance advantages of 

hardware implementations with the ease of development 

of software implementations. 

The new Anemone floating point processor from 

BittWare connects to the FPGA via high-rate, low latency 

link ports. All access to off-chip memory is through 

the FPGA, as are off-board interfaces, such as PCIe 

backplanes or Ethernet ports. The Anemone processor 

is a multi-core design, currently offering 16 cores 

per chip, all interconnected in a mesh network with a 

shared memory model. Each core has 32 Kbytes of local 

memory, supports IEEE-754 floating point processing, 

and is individually programmable using ANSI-C. The 16core 

Anemone chip offers 32 GFLOPS, while consuming 

only two watts of total power. Four Anemone chips, 

providing 128 GFLOPS, are available on an FMC (VITA 

57) standard daughter card for use on FPGA host boards 

such as AMC, PCIe, and VPX. These are available today 

with Altera high end Stratix IV FPGAs, as shown in Figure 

2, and will be offered later this year with Stratix V FPGAs. 

The Anemone-to-FPGA interface is made transparent 

to the application using BittWare’s ATLANTiS 

FrameWork, which can bolt up seamlessly to Altera’s 

QSys FPGA system interconnect tool. This facilitates 

optimal partitioning of processing tasks between the 

Anemone and FPGA. With up to one TeraFLOPS of 

hardware floating point processing on Stratix V FPGAs, 

and 128 GLOPS of software floating point processing 

on Anemone, extremely high computational rate 

applications can be implemented in a low form factor, 

low power consumption platform. 

An example application might be high-performance 

airborne radar systems. The FPGA can implement the 

digital downconversion, beamforming, MTI filtering, 

Doppler FFT processing, pulse compression, and 

matrix inversions needed in space-time adaptive 

processing (STAP). The Anemone processor is ideal 

for lower GFLOPs but more complex tasks. Examples 

of this are CFAR detection processing, computing beam 

forming coefficients, adapting and controlling radar 

modes, and transmit waveform generation. Low latency 

between the processing sub-systems is essential, and 


TECHNICAL ARTICLE


LEDs 

ANENOME 

Floating Point 

Co-Processor 

ANENOME 


Co-Processor 

ANENOME 


Co-Processor 

ANENOME 


Co-Processor 

DDR3 SDRAM 

(up to 1 GB) 32 

DDR3 SDRAM 

(up to 1 GB) 32 

Link Ports 

Clocks, I2C, JTAG, Reset 

Figure 2: Anemone-Stratix High Performance Floating Point Processing System featuring an AAFM co-processing mezzanine on an S4-3U- 

VPX. 

these requirements are not easily met with GPU or CPU 

architectures. The combination of Anemone and Stratix 

FPGAs offer an ideal balance of TeraFlops processing 

power, flexibility to partition across hardware and 

software implementation, high GLOPS/Watt, and a very 

compact form factor. 

This combination can also be ideal for any embedded 

application requiring high-performance computing 

power in military, medical imaging, wireless, or test 

equipment applications. Through the choice of FPGA 

and number of Anemone chips, the design can easily 

scale the level of processing power. The availability of 

Anemone-Stratix systems on BittWare’s COTS boards 

and systems supports rapid product development 

cycles. 

RS-232 

JTAG 

Header 

About the Author 

Michael Parker received his MSEE from Santa Clara 

University in California, and his BSEE from Rensselaer 

Polytechnic Institute in New York. He has over 20 years 

of DSP wireless engineering design experience with 

companies such as Alvarion, Soma Networks, TCSI, 

Stanford Telecom, and numerous startup companies. 

Michael joined Altera in January 2007, and is responsible 

for Altera’s entire digital signal processing (DSP) product 

planning. 

Michael authored a book entitled Digital Signal 

Processing 101, published in 2010 and has written and 

published over 20 technical articles on DSP, floating 

point, and various other technology subjects. ■ 


Control 

Port 

FINe 

Bridge 

Data 

Port 

FPGA 

Stratix IV GX 

(4SGX230/530) 

FLASH 

Supported by: 

ATLANTiS Framework 

Serdes 

GigE 

10/100 Ethernet (Build Option) 

32 

32 

4x 

4x 

4x 

3x 

DDR3 SDRAM 

(up to 1 GB) 

DDR3 SDRAM 

(up to 1 GB) 

32 LVDS pairs 

4 bits DIO or RS 232/RS422 

(Build Options) 

4 bits DIO 

(Build Option without 10/100 Eth.) 

(sRIO, PCIexp, 10GigE) 

P0 

P1 

P2 

TECHNICAL ARTICLE

System Perspective 

on Specifying Electronic 

Power Supplies: 

Bob Stowe 

Power Supply Design Consultant 

Load 

Characterization 

In a previous issue (Issue 19) we introduced the topic of 

“A System Perspective on Specifying Electronic Power 

Supplies.” In this article we will learn about the effect of 

the load on specifying a power supply. 

The following drawing shows a power supply in a 

very simplified form, connected to a simplified load. 

The feedback and control circuit measures the output 

voltage, compares it to a reference (not shown), and 

adjusts the source voltage to maintain the load voltage 

constant. This process is not perfect, and the power 

supply specifications describe the deviation from 

perfection. The deviation from perfection must be within 

the requirements demanded by the load for the load to 

operate satisfactorily. 

The Importance of 

Understanding the Load 

The load imposes a major portion of the performance 

requirements on the power supply. The power supply is 

never a perfect black box and it is extremely important 

to treat it as a vital and integral part of your system. It 

must meet the demands placed upon it by the load in 

several key performance measures. The most common 

measures are discussed below: 

Static Requirements 

Typically, the load requires one of the following 

parameters to be provided and controlled to within 

a certain tolerance band: voltage, current, or power. 

The other two parameters which are not controlled 

would be called compliance parameters. For example, 

a subassembly might be designed to operate with a 

controlled input voltage of 5 volts. When excited with 

a controlled input voltage of 5 volts, the subassembly 

responds by drawing up to 10 amperes, and consuming 

up to 50 watts of power. This means that the power supply 

must maintain the output voltage at 5 volts and be able 

to provide up to 10 amperes of current, since up to 10 

amperes is what the load draws when excited by 5 volts. 

In this case, power is an alternate way of expressing 

compliance because power is the same as voltage times 

current. 

EEWeb | Electrical Engineering Community Visit www.eeweb.com 13


Some loads may require different controlled parameters 

at different times. Such an example is a battery charger 

which might require constant current for battery charge 

mode and constant voltage for battery maintenance 

mode. 

Loads will require the controlled parameter to be within a 

certain tolerance band for proper operation. The power 

supply must maintain the controlled parameter within 

the tolerance band. 

These parameters may be expressed in terms of average, 

RMS, or a peak value with a duration qualifier. 

Dynamic Requirements 

Loads also exhibit dynamic characteristics which change 

over time. 

Time Transients 

Many types of loads frequently change their effective 

impedance. Such an example might be a computer 

printer which exhibits rapid step changes in effective 

impedance. For such a device to function properly, the 

power supply must be able to rapidly source spurts 

of output current while maintaining the output voltage 

within a specified band. This means that the power 

supply must have enough output capacitance and high 

enough control loop bandwidth to maintain the output 

Vsource 

Power Supply 

Zout 

Feedback 

and 

Control 

Figure 1: Simplified representation of power supply and load. 

voltage within the prescribed limits. Loads which have 

this type of behavior must have power supplies specified 

to limit the droop on the leading edge of the pulse, and 

recover to within a certain band of the steady state output 

in a prescribed time interval. 

Voltage Dependence 

Non-linear loads change impedance as voltage is 

increased. One example is a typical solid-state circuit 

which might draw very little current at low voltages, 

and then begin to draw current with a very rapid and 

nonlinear increase as voltage is increased. 

A more problematic configuration is cascading a power 

supply with a second power supply of a switching 

converter design. A switching converter has a nonlinear 

negative resistance characteristic. At very low input 

voltages, below the turn-on threshold, the current may 

be miniscule. When the input voltage is increased to 

the turn-on threshold, the input current suddenly draws 

very high current. As the input voltage is increased, the 

input current decreases, following a constant power 

characteristic. If care is not taken in the first power 

supply design and cable length, the load (the switching 

converter) will cycle on and off because of the voltage 

drop in the cable length and/or the output impedance of 

the power supply. 


Iload 

Zload 

+ 

Vload 

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TECHNICAL ARTICLE


Frequency Dependence 



Loads can create a frequency dependence which 

is not obvious to the untrained user. This frequency 

dependence is of at least two forms: 

1. Resonant behavior can occur due to inductance and 

capacitance in both the power supply and the load. 

It is possible for power supplies to resonate with 

load capacitance or inductance if the power supply 

is not designed well for the load. This resonance 

will usually take place at frequencies determined 

by the reactive elements in the system. This effect is 

usually undesirable unless the system is designed to 

be resonant. 

2. The power supply control loop behavior can be 

adversely influenced due to load capacitance and 

inductance. The presence of substantial capacitance 

or inductance can move the control loop poles and 

zeros, substantially changing the transient response 

and ripple rejection capability of the power supply 

by decreasing or possibll increasing the bandwidth 

of the power supply. 

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Temperature Dependence 

Loads must operate in their intended environment. More 

often than not, the power supplies for these loads must 

operate in the same environment. These environments 

may be benign, such as a test laboratory, or severe, 

as in down-hole oil and natural gas exploration. The 

power supply must be able to work in the environment 

of the load, or the power supply environment must be 

separated from the load to allow satisfactory operation. 

About the Author 

Bob Stowe has over 21 years of experience in various 

disciplines related to electronic energy conversion, 

possesses a master’s degree in power electronics, 

and is a member of IEEE in good standing. He also 

has obtained his certification in power electronics from 

the University of Colorado (COPEC). Additionally, he 

graduated from the United States Naval Academy in 1984 

with a bachelor’s degree in electrical engineering, and 

served for five subsequent years as a United States Naval 

Officer. As a former military officer, he is familiar with 

military project requirements. Bob now works for True 

Power Research as a Power Supply Design consultant. ■ 


TECHNICAL ARTICLE

High Efficiency 5V, 10A Buck Regulator 

ISL95210 

The ISL95210 is a high-efficiency step-down regulator that can 

deliver 10A of output current from a 5V input. The small 

4mmx6mm QFN package and only four external components 

provide a very small total solution size. Low resistance internal 

MOSFETs deliver excellent efficiency and permit full power 

operation in a +90°C ambient without airflow. 

The regulator operates from an input voltage of 2.97V to 5.5V, 

and provides a 0.6% accurate output voltage over the full 

operating temperature range. Intersil's patented R4 control 

architecture provides exceptional transient response with no 

external compensation components. The output voltage may be 

programmed by an internal DAC or by an external resistor divider 

(see “Output Voltage Programming” on page 11 for more 

details). 

Several digital control signals provide flexibility for users that 

want additional features. Switching frequency, switching mode, 

output voltage margining and daisy-chained power-good 

functions are all programmed by these pins. The ISL95210 also 

includes comprehensive internal protection for overvoltage, 

undervoltage, overcurrent and over-temperature conditions. 

Related Literature 

• See AN1485, “ISL95210 10A Integrated FET Regulator 

Evaluation Board Setup Procedure” 

VIN = 5V 

CONTROL 

SIGNALS 

CIN 

10µF 

VCC 

VIN 

PVCC 

EN 

PG_IN 

FSET 

VSEL1 

MPCT 

MSEL 

VSEL0 

FCCM 

PGOOD 

PHASE 

VOUT 

VCC 

AGND 

PGND 

T-PAD 

LOUT 

420nH 

VOUT = 1.2V 

COUT 

220µF 

FIGURE 1. 10A DC/DC CONVERTER USING ONLY 4 EXTERNAL 

COMPONENTS 

November 17, 2011 

FN6938.3 

ISL95210 

FSW= 800kHz 

1µF 

+ 

POWER GOOD 

LOUT = MPC0740LR42C (NEC/TOKIN) 

COUT = 2TPLF220M5 (SANYO) 

Features 

• 10A Continuous Output Current 

• 2.97V to 5.5V Input Voltage Range 

• Up to 95% Efficiency 

• Full Power Operation in +90°C Ambient without Airflow 

• R4 Control Architecture Delivers Excellent Transient 

Response Without Compensation 

• Pin Selectable Output Voltage Programming 

• ±0.6% Output Voltage Accuracy Over Full Operating 

Temperature Range 

• Programmable Enhanced Light-Load Efficiency Operation 

• Output Voltage Margining and Power-good Monitor 

• Small 6mmx4mm QFN Package 

Applications 

• Point-of-Load Power Supplies 

• Notebook Computer Power 

• General Purpose Power Rail Generation 

EFFICIENCY (%) 

100 

95 

90 

85 

80 

75 

70 

65 

Get the Datasheet and Order Samples 

http://www.intersil.com 

60 

55 

50 

VIN = 5V 

VOUT = 1.2V 

FSW = 800kHz 

0 1 2 3 4 5 

IOUT (A) 

6 7 8 9 10 

FIGURE 2. EFFICIENCY OF CIRCUIT SHOWN IN FIGURE 1 

(INCLUDES INDUCTOR LOSSES) 

Intersil (and design) is a registered trademark of Intersil Americas Inc. Copyright Intersil Americas Inc. 2011 

All Rights Reserved. All other trademarks mentioned are the property of their respective owners.

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Brett Fox - EEWeb

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