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A S P E C I A L S U P P L E M E N T T O E D N

N O V E M B E R 2 0 0 5



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www.power-one.com 800.678.9445 805.987.8741

A Digital Power RevolutionA Digital Power Revolution

Z-One Digital IBA Integrates Power Management and Conversion System-level component count reduction improves cost, reliability, and power density.

GUI configuration and simulation dramatically simplifies power system development.

Industry-leading power conversion and management capabilities include programmable

output voltages, sequencing, tracking, and protection limits.

Vout 1 Vout 2 Vout 3(Up to 32 Outputs)

48V

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IBA

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Z-Series Digital Power Manager Programs and manages Z-POL converters.

Monitors intermediate bus, accepts externalinterrupts, and initiates crowbar protection.

Facilitates Z-POL performance telemetry forremote monitoring and fault management.

Z-POL (Point-Of-Load) Converters Programmable 0.5 to 5.5VDC outputs

using 3.0 to 13.2VDC inputs.

Current densities up to 39 amps/in2.

Real-time reporting capabilities includevoltage, current, and temperature.

90% Reduction in Components, PCB Traces, and Development Time

Power-One and the Power-One logo, Z-One, ZIOS, Z-POL, and the Z Digital IBA logo are trademarks or registered trademarks of Power-One, Inc.
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3/36Enter xx at www.edn.com/infoEnter xx at www.edn.com/info
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A L L T H I N G S E L E C T R O N I C S T A R T W I T H M I C R O C H I P

The Microchip name and logo, the Microchip logo and PIC are registered trademarks of Microchip Technology Incorporated in the USA and in other countries. PICkit is a trademark of Microchip Technology

Incorporated in the U.S.A. and other countries. 2005 Microchip Technology Incorporated. All rights reser ved.

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Reed Business Information225 Wyman Street, Waltham, MA 02451

Phone: (781) 734-8000www.edn.com

EDNWorldwideStephen Moylan, President,

Boston Division/Publishing Director

Phone: (781) 734-8431Fax: (781) 290-3431

[email protected]

Cindy Fitzpatrick, Director

EDNCustom Publishing Services

Phone: (781) 734-8438Fax: (781) 290-3438

[email protected]

Heather Wiggins

Web/CPS Production Coordinator

Phone: (781) 734-8448Fax: (781) 290-3448

[email protected]

Contributing Editors:

Linnea C. BrushSenior Research Analyst

[email protected]

Jeremiah BryantResearch Analyst

[email protected]

Jeff ShepardPresident

[email protected]

A D V E R T I S E R I N D E X

American Power Design . . . . . . . . . .P24

Bear Power Supply . . . . . . . . . . . . . .P24

Bel Fuse . . . . . . . . . . . . . . . . . . . . .P19

Darnell Group . . . . . . . . . . . . . . . . . .P6

Digi-Key Corporation . . . . . . . . . . . . . .P3

Fairchild Semiconductor . . . . . . .Cover 4

Gaia Converters . . . . . . . . . . . . . . . .P30

International Rectifier . . . . . . . . . . . .P11

Intersil . . . . . . . . . . .P8, 21,26, Cover 3

Kepco Inc . . . . . . . . . . . . . . . . . . . .P29

Linear Technology Corporation . . . . . .P25

Martek Power . . . . . . . . . . . . . . . . .P15

Micrel . . . . . . . . . . . . . . . . . . . . . . .P28

Microchip Technology Inc . . . . . . . . . .P4

National Semiconductor . . . . . . . . . . .P7

Norvell Electronics . . . . . . . . . . . . . .P23

Power Integrations Inc . . . . . . . . . . .P12

Power-One . . . . . . . . . . . . . . . . .Cover 2

Spellman High Voltage . . . . . . . . . . .P20

Vicor . . . . . . . . . . . . . . . . . . . . . . . .P31

PART FOUR: EMBEDDEDPOWER 6Letter from the Editor

9Embedded PowerSupplies Reach New Heights

13CASE STUDY:

LINEAR TECHNOLOGY CORPORATION

How to Provide a Full-featured

Embedded POL DC/DC Converter

16AC Powering

Semiconductor Growth

18CASE STUDY:

TEXAS INSTRUMENTSScalable Power Systems Meet the Needs

of Configurable Blade Servers

22CASE STUDY:

FAIRCHILD SEMICONDUCTOR

PFC/PWM Combo IC Enables Best Power and

Board Space Efficiency in LCD TVs

27CASE STUDY:

POWER-ONE, INC.

Which Voltage Bus is Best?

Review the EDN Embedded Power

and Control Online Source List atwww.edn.com/supplements

NOVEMBER 2005 EDN POWER TECHNOLOGY P5


6/36P6 EDN POWER TECHNOLOGY NOVEMBER 2005


P A R T F O U R : E M B E D D E D P O W E R

he market for embedded ac-dc power supplies and dc-dc converters is currently being driven by a number of technologies,including blade servers, Power-over-Ethernet (PoE), and the intermediate bus architecture (IBA). Combined with digital powermanagement and control, opportunities are emerging for higher wattage converters.

Blade servers are seeing growth that is more than three times faster than the server market as a whole, and their growth isone driver pushing the IBA. As a result, large original equipment manufacturers that were reluctant to move towards the IBA are

now employing it in their higher performance systems. In this issue, Texas Instruments discusses how they helped a customer design ascalable power system to meet the needs of configurable blade servers.

Both space and cooling are at a premium in networking systems powered via a 48V backplane. Therefore, it is extremely important forpoint-of-load converters to be both compact and efficient. Linear Technology provides a case study on supplying a POL dc-dc converter forembedded systems that meets or exceeds the multiple constraints of limited space and cooling within a given enclosure.

Powering challenges on the ac input side are equally demanding, with power factor correction (PFC), hot swappability, and pulse widthmodulation (PWM) posing special challenges. Semiconductor companies are providing products for this side of the house that range fromdigital PWM to One Cycle Control for PFC.

PFC, in particular, is gaining attention as new harmonic standards become mandatory in Europe and Japan, and efficiency programs(such as Energy Star) prescribe limits to power consumption. To address PFC regulations, Fairchild Semiconductor designed a PFC/PWMcombo integrated circuit to enable power and board space efficiency in LCD televisions.

As regulations change, and as digital power moves into the commercial mainstream, opportunities will emerge for power supplymanufacturers to increase efficiency and reduce costs. Power-Ones case study looks at how they helped a customer choose the rightintermediate bus voltage by using a digital power management system. The variety of solutions being offered, and the standards to supportthem, ensure that embedded power supplies will remain one step ahead of system needs.

LINNEA C. BRUSHSenior Research AnalystDarnell Group

LETTER from the EDITOR



National Semiconductor Corporation, 2005. National Semiconductor, , and LLP are registered trademarks of National Semiconductor Corporation.

All rights reserved.

New Alternatives for Next-GenerationDC-DC Conversion

Alternative 2:LM5033 Intermediate Bus Converter (IBC)

Isolated step-down converter stage feeds multiplenon-isolated point-of-load (POL) converters

Each output is independently regulated

No feedback opto-coupler required

Integrated start-up regulator

Low primary component count Tiny, thermally enhanced LLP packaging

Buck stage regulates input to push-pull or

full-bridge isolation stage Accommodates wide input voltage range

No output filter inductors required

Lower voltage stress and switching loss inpush-pull switches

Ideal for multiple high-power outputs

Optimized for synchronous rectification

Alternative 1:LM5041 Current-Fed Converter

For FREE samples, evaluation boards,

datasheets, and more, visit us today at:

power.national.com

Or call 1-800-272-9959

Whatever Topology You Choose, National Has the Power Management Solution

LM5041 Current-Fed Converter

LM5033 IBC
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Intersil High Performance Analog

Intersil Switching Regulators

Intersil Switching Regulators for precise power delivery.2005 Intersil Americas Inc. All rights reserved. The following are trademarks or services marks owned by Intersil Corporation

or one of its subsidiaries, and may be registered in the USA and/or other countries: Intersil (and design) and i (and design).

The first line of defenseagainst heat is athermally-efficient HTSOP-28package, which utilizes an

exposed thermal padunderneath the IC to spreadheat through the PCB.

The VTJ pin is a

formula-based, accurate

indicator of the internal

silicon junction temperature.

If all else fails and the

temperature sensor indicates

a junction temperature above

135C, the PWM Regulatorwill shut down.

Key Features:

4A (EL7554) and 6A (EL7566)

continuous output current

Up to 96% efficiency

Built-in 5% voltage margining

3V-to-6V input voltage

0.58 in2 (EL7554) and 0.72 in2

(EL7566) footprint with

components on one side

of PCB

Adjustable switching frequency

to 1MHz

For more information and samples,

go to www.intersil.com/edn

Easy-to-use simulation tool also

available. Modify switching frequency,

voltage ripple, ambient temperature

and view schematics waveforms,

efficiency graphs and complete BOM

with Gerber layout.

www.intersil.com/iSim

Whats Black, White,and Cool All Over?Maintaining IC temperatures doesnt have tobe a riddle. Intersil's new high currentIntegrated FET Regulators have the industry'sonly true Thermal Protection with auto shutdown at 135C.

Intersil's EL7554 and EL7566 DC-DC buck regulators with internal

CMOS power FETs operate from 3V-to-6V input voltage and are

capable of up to 96% efficiency. But what's really cool about these

devices is ground breaking features like built-in Thermal Protection

and Voltage Margining for actual in-circuit performance validation.
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9/36NOVEMBER 2005 EDN POWER TECHNOLOGY P9

number of trends are converging that

are pushing embedded ac-dc power

supplies and dc-dc converter modules

towards higher wattages. Rapidly grow-

ing blade servers, Power-over-Ethernet (PoE) equip-

ment and several other devices are driving power

requirements higher. Shifting bus architectures have

an even larger effect on the embedded power supply

market. These shifts range from the growing usage of

the intermediate bus architecture (IBA), to alternative

powering trends, to the biggest potential change

digital power control and management. Combined,

these trends are driving opportunities for higher

wattage converters.

Gains made by the IBA and its hallmark busconverters are a primary driver of this trend. While

the IBA is clearly not new, the market acceptance of

the IBA is continuing to grow. Large OEMs that were

reluctant to move towards the IBA are now employing

it in their higher performance systems. Blade servers

are seeing growth that is more than three times faster

than the server market as a whole. Currently blades

account for a small portion of the server market, their

growth is one driver pushing the IBA.

Recently, a number of companies have released

new bus converters that illustrate growing interest in

the IBA. Power-One added a 46A quarter-brick bus

converter to its product line that delivers 441W. Tyco

Electronics introduced the QBK033 bus converter,

which the company claims

was the first 400W quarter-

brick power module. Artesyn

Technologies increased the

wattage of its highest power

quarter-brick bus converter to

450W, a 150W improvement

over its earlier generation

quarter-brick bus converter.

Similarly, the growing

usage of the IBA is driving

sales of Point-of-Load (POL)converters. The worldwide

non-isolated dc-dc converter

market, including POLs and

voltage regulator modules, is

outpacing the dc-dc converter

market as a whole. According

to the Darnell Group, rev-

enues in this market are projected to rise from $760

million in 2005 to $1.4 billion in 2010. A number of

new product offerings from companies in the Point-of-

Load Alliance (POLA) illustrate this trend.Ericsson Power Modules recently introduced 17

POLA-interoperable POLs in three platforms with cur-

rent ratings from 6A to 60A. One of these POL fami-

lies, the PMM series, is aimed at current-thirsty high-

end computer applications. It delivers 60A, while

achieving a 96% peak efficiency. Artesyn has devel-

oped 50A and 60A POL converters for the telecom

and datacom markets including blade servers, data

storage switches and voice-processing systems.

Texas Instruments has introduced the PTVxx010 8A

and PTVxx020 18A families of POLA compatibleplug-in power modules. While POLs are not specific

to the IBA, the growth of POLs coupled with the



Embedded PowerSupplies Reach New Heights8 byJEREMIAH BRYANT

500W

2005 2010

2000

1500

1000

500

0

Worldwide DC-DC converter module market by wattage(millions of dollars)

Figure 1: Artesyn increased the power ofits latest Typhoon quarter-brick bus

converters to 450W


10/36

expanding bus converter market illus-

trates the growing usage of the IBA.

While the IBA is creating architectur-

al power shifts within the system's box,

PoE is changing power requirements out-

side of the box. Like the IBA, PoE is

changing the power distribution mecha-

nism from the wall plug to the load. In PoE, power sourc-

ing equipment (PSE), typically either a PoE endspan inte-

grated into an Ethernet switch or a PoE midspan, deliver

power to a powered devices (PD), such as a VoIP phone,

Wi-Fi access point, flat panel PC and so on.

The PoE strategy increases power requirements

for the centralized PSE, especially for ac-dc front

ends, but typically replaces the power supplies for the

PDs with discrete components. Currently, PoE deliv-

ers only a maximum of 15.4W per port, which limits

the type of PDs that PoE can power and also limits

the power requirements of the PSE. However, the

IEEE has formed a study group that is examining

PoE-Plus, with the goal of at least doubling the power

level to 30W per port and possibly as high as 100W.

If PoE-Plus gains steam, ac-dc front ends will see a

greater opportunity, as will dc-dc converter modules.

Trying to capitalize on the growing PoE market,Astec Power has introduced the DS657, a 657W

power supply for PoE implementations. Phihong has

introduced a 275W power supply with integrated 24-

port PoE injection. Power Integrations has designed

new solutions for the PoE market, as they expanded

their DPA-Switch family

of ICs to include an option

for PoE.

The growing IBA mar-

ket is also yielding opportu-

nities for digital power con-trol and conversion

because systems that use

this architecture are going

to be the early digital

adopters. Thus far there

have been two primary dig-

ital implementation strate-

gies. The first strategy is

Power-One's proprietary Z-

One Digital IBA which is

a complete digital product line for the IBA. The sec-ond approach stems from the PMBus which

defines a standard way to communicate with power

converters using the SMBus in

order to configure, control and

monitor PMBus compatible

devices, such as converters or

power supplies. However, the

PMBus is only a communica-

tions standard and companies

are still developing complete digital power conversion

product lines. While there are a number of differences

between the two approaches, the primary difference

stems from the communications protocols and the

manner in which the parameters are set.

Power-One has two digital strategies. The first

strategy is the I2C pro-

grammable Z-7000 POLs

which are programmed

using the company's pro-

prietary software and can

be reprogrammed at any

time. Power-One's addi-

tional strategy is the one

time programmability

found in the Z-1000 No-

Bus POLs. These POLs

provide power management capabilities without hav-ing to implement external controllers and other asso-

ciated components.

Another digital communications approach origi-

nated from a collaborative open standardthe PMBus.

So far, Texas Instruments, Zilker Labs and Silicon Labs

have digital power controllers, but PMBus-complaint

digital dc-dc converters are just now hitting the market.

Several new digital products were unveiled at the

Digital Power Forum or shortly after. Artesyn Tech-

nologies announced a PMBus-compliant digitally pro-

grammable dc-dc converter. The DPL20C is a non-iso-lated POL that features digital configuration, monitor-

ing and diagnostic facilities accessible via the PMBus

interface. The 20A POL provides a programmable out-

put voltage from 0.6V to 5.5V, programmable sequenc-

ing, tracking and margining and real-time voltage, cur-

rent and temperature monitoring. Astec's first offering

from its Digital Power Initiative is the PMBus-complaint

DTX dc-dc converter. The DTX features integrated dig-

ital control with bi-directional PMBus communications

and includes self-diagnostics, efficiency optimization

and output impedance control in addition to dynamic

P10 EDN POWER TECHNOLOGY NOVEMBER 2005



Figure 3: Power-One has expanded itsZ-1000 No-Bus family to include 7A,

15A and 20A POLs

(Embedded Power continued on P33)

Figure 4: Astec Powers first offering from itsDigital Power Initiative is the 50W DTX dc-dcconverter, which features integrated digital

control with bi-directional PMBuscommunication

Figure 2: Ericsson power modulesintroduced 17 POLA-interoperable POLs

capable of delivering 6A to 60A


11/36Enter xx at www.edn.com/infoEnter xx at www.edn.com/info THE POWER MANAGEMENT LEADER

CAN YOUR BRICK DO THIS?

for more information call 1.800.981.8699 or visit us atwww.irf.com/dcdc

IRs DC Bus Chipset Enables Bricks With 48Vin, 9.6Vout, 330W at 97% Efficiency

International Recti f ier s new power

management DC Bus converter chipset

delivers 48V in , 9.6Vou t, over 330W at

97% efficiency for networking and

telecommunications systems.

Single DirectFET MOSFET can replace

two SO-8 devices

Reduces component count by > 45%

Achieves up to 1.5% better efficiency

compared to industry standard quarterbrick form factors

Reduces temperatures up to 40C

Board space reduced by 29% vs. quarter

brick form factors

Industry Best RDS(on) for IRF6644 (13m),

IRF6646 (9.5m), IRF6635 (1.8m)

Design Services available at www.mypower.com

New DC-DC Chipset Solution from International RectifierDirectFET MOSFETs

Part # Package VDSS RDS(on) max QG QGD

@ VGS=10V Typical TypicalIRF6644 Medium can 100V 13m 35nC 11.5nC

IRF6655 Small can 100V 62m 8.7nC 2.8nC

IRF6646 Medium can 80V 9.5m 36nC 12nC

IRF6613 Medium can 40V 3.4m 42nC 12.6nC

IRF6614 Small can 40V 8.3m 19nC 6.0nC

IRF6635 Medium can 30V 1.8m 47nC 17nC

Control IC

Part # Package Voltage Rating Description

IR2085S SO-8 100VPrimary-side half-bridge control IC,fixed 50% duty cycle, self-oscillating

IR2086S SO-16 100VPrimary-side full-bridge control IC,

fixed 50% duty cycle, self-oscillating

#

#

#

# IR product featured in Full-Bridge Bus Converter reference design above

Full Bridge DC Bus Converter

98

96

94

92

90

88

86

84

820 5 10 15

Load Current (A)

Full-Bridge Bus Converter Chipset (IRF6646, IR2086S, IRF6635 )48Vin/ 9.6Vout/ 175kHz

ElectricalEfficiency

(%)

20 25 30 35

4 x (80V) IRF6646 Primary2 x (30V) IRF6635 Secondary

97%

IR's proprietary DirectFET technology is covered by US Patent 6,624,522 and other US and foreign pending patent applications.DirectFET is a trademark of International Rectifier.

ReferenceDesignsAvailable
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http://www.powerint.com/puzzler8http://www.powerint.com/puzzler8http://www.powerint.com/puzzler8





thesolutionFeature Rich IC Allows Optimum Flexibility

The penalty for poor tracking or sequencing is often

irreparable damage to devices in an embedded

system. FPGAs, PLDs, ASICs, DSPs

and microprocessors typically have

diodes placed between the core and

I/O supplies as a component of ESD

protection. If supplies violate the track-

ing requirements and forward bias the

protection diodes, the device may be

damaged.

Voltage sequencing, tracking, and margininghave become popular features in dc-to-dc convert-

er modules; however, these functions are less com-

monly found in dc/dc controller ICs. Linear

Technologys LTC3770 is an ideal solution for POL

dc/dc conversion needs and is also distinguished by

its fast transient response, a phase-locked loop

(PLL) that allows synchronization to a system clock,

and a highly accurate reference. Capable of operat-

ing from a 4V to 32V input, the current-mode con-

troller can produce a stepped down output at cur-

rents up to about 25A, see Figure 1.The LTC3770s constant on-time, valley cur-

rent-mode architecture, combined with a very low

minimum on-time (50ns typical), allows the control

loop to respond quickly to load steps. The LTC3770

can perform RDS(ON) current sensing by sensing the

voltage drop across the synchronous power MOS-

FET. Or for systems requiring more-precise control

of output current, a conventional sense resistor can

be used in the source of the lower MOSFET. In

either case, the current limit is user-programmable.

The controller can operate at very low dutycycles. In the extreme case, an output as low as 0.6V

can be supplied from input voltages as high as 32V -

New ICs Simplify Embedded POLDC/DC Converter Designs

8 byTONY ARMSTRONG, PRODUCT MARKETING MANAGER,

POWER PRODUCTS GROUP, LINEAR TECHNOLOGY CORPORATION

thechallengeMost embedded systems are powered via a 48V back-plane. This voltage is normally stepped-down to a lower

intermediate voltage of either 12V or 5V to allow power

to the racks of boards within the system. However,

most of the sub-circuits or ICs on these boards are

required to be powered at voltages ranging from 0.8V

to 3.3V at currents ranging from tens of milliamps to

tens of amps. As a result, a point-of-load (POL) dc/dc

converter is needed to step down the 12V or 5V to the

desired voltage and current level required by the sub-

circuits or ICs.

Since space and cooling are at a premium in

these systems, it is extremely important for any POLconverters to be both compact and efficient.

Furthermore, many microprocessors and digital signal

processors (DSPs) need a core power supply and an

input/output (I/O) power supply which must be

sequenced during start-up. Designers have to consider

the relative voltage and timing of core and I/O voltage

supplies during power-up and down operations to

comply with manufacturers specifications. Without

proper power supply sequencing, latch-up or excessive

current draw may occur that could lead to damage to

the microprocessors I/O ports or the I/O ports of a sup-

porting device, such as memory, programmable logicdevices (PLDs), field programmable gate arrays

(FPGAs), or data converters. To ensure that the I/O

loads are not driven until the core voltage is properly

biased, tracking of the core supply voltage and the I/O

supply voltage is necessary.

Although start-up and shutdown tracking can be

implemented externally for any given DC/DC converter,

the power supply sequencing requirements will vary

from system-to-system. These solutions include appli-

cation specific standard products (ASSPs) that can be

configured via a programmable interface or by external

components; programmable microcontroller-based

solutions and FPGA solutions.

CUSTOMERPROFILEA WORLDWIDELEADER INNETWORKINGSOLUTIONS FORTHE INTERNET

CASE Study





Figure 1. The LTC3770 steps down a 12V input to a 2.5-V output at 10 A

even under no-load conditions. In the applications

where such low output voltages are required, the pre-

cision of the chips voltage reference becomes signifi-

cant. The LTC3770 specifies an output voltage accu-

racy of 0.5% at room temperature and 0.67% from

0C to 85C. Across the devices full operating tem-perature range (40C to 85C), the total error on out-

put voltage is still only 1%.

The controllers operating frequency can be select-

ed by a single external resistor. For applications that

require stringent constant-frequency operation, a PLL

(phase lock loop) allows the LTC3770 to be synchro-

nized to an external clock, which helps reduce EMI.

In normal operation, the top MOSFET is turned

on for a fixed interval determined by a one-shot timer.

When the top MOSFET is turned off, the bottom

MOSFET is turned on until the current comparatorICMP trips, restarting the one-shot timer and initiating

the next cycle, refer to Figure 2. Inductor current is

determined by sensing the voltage between the

SENSE+ (PGND on the SSOP package) and SENSE-

(SW on the SSOP) pins using a sense resistor or the

bottom MOSFET on-resistance. The voltage on the ITHpin sets the comparator threshold corresponding to

inductor valley current. The error amplifier EA adjusts

this voltage by comparing the feedback signal VFBfrom a reference voltage set by the VREFIN pin. If the

load current increases, it causes a drop in the feed-back voltage relative to the reference. The ITH voltage

then rises until the average inductor current again

matches the load current.

At low load currents, the inductor current can

drop to zero and become negative. This is detected

by the current reversal comparator IREV which then

shuts off M2, resulting in discontinuous operation.

Both switches will remain off with the output capaci-

tor supplying the load until the ITH voltage rises abovethe zero current level (0.75V) to initiate another cycle.

Discontinuous mode operation is disabled by com-

parator F when the PFB pin is brought below 0.6V,

forcing continuous synchronous operation.

The operating frequency is determined implicitly

by the top MOSFET on-time and the duty cycle

required to maintain regulation. The one-shot timer

generates an on-time that is proportional to the ideal

duty cycle, thus holding the frequency approximately

constant with changes in VIN. The nominal frequency

can be adjusted with an external resistor RON.Over-voltage and under-voltage comparators OV

and UV pull the PGOOD output low if the output feed-

back voltage exits a 10% window around the regu-

lation point after the internal 25s power bad mask

timer expires. Furthermore, in an over-voltage condi-

tion, M1 is turned off and M2 is turned on immedi-

ately and held on until the over-voltage condition

clears.

Foldback current limiting is provided if the out-

put is shorted to ground. As VFB drops, the buffered

current threshold voltage ITHB is pulled down andclamped to 0.9V. This reduces the inductor valley

(New ICs Simplify continued on P32)


http://www.martekpower.com/http://www.martekpower.com/http://www.martekpower.com/


16/36

mbedded power is used in a wide range

of distributed power architectures with

much of the design focus going to the

dc output side. Challenges on the ac

input side are equally demanding, however, including

power factor correction (PFC), hot swappability, and

pulse width modulation (PWM). Semiconductor com-

panies are providing products for this side of the

house that range from digital PWM (DPWM) to OCC

(one cycle control) for PFC.

PFC (power factor correction) is gaining attention

as new harmonic emission standards become manda-

tory in Europe and Japan. Other countries are at vari-

ous stages in accepting these standards which means

power supplies could be subject to more stringentrequirements. High minimum power factors are no

longer limited to high-power applications, for instance.

Newer norms and standards apply to products dissi-

pating as little as 75W or 26W for lighting devices.

Low PF results in poor electrical efficiency creat-

ing the need for larger generators, transformers and

other distribution devices that would otherwise not be

necessary. Other PF conditions include overloads,

voltage distortions, noise, parasitic harmonics in the

network, and

reciprocal inter-ference in the

system.

Analog-based

PFC control

methods have

long been used

in power sup-

plies. One PFC

control method

gaining in pop-

ularity is to usean analog controller with a discontinuous conduction

mode, such as Fairchild Semiconductors FAN7527B

and FAN4812. The company also introduced its new

FSAB20PH60 PFC smart power module which

implements the partial PFC switching converter cir-

cuit topology, switching at twice the line frequency of

the traditional PFC topology. The partial-switching

method is popular for 1kW to 3kW air conditioners.

International Rectifier introduced the IR1150

family of PFC integrated circuits for ac-dc PFC

circuits. IR utilizes its licensed OCC approach in the

IR1150 to deliver the perform-

ance of continuous conduction

mode (CCM) PFC with the sim-

plicity, reliability, and low compo-

nent count of a discontinuous

current mode circuit for PFCapplications. The company

claims that the patented OCC

technique radically alters tradi-

tional thinking about PFC solu-

tions. Its a form of CCM PFC

using a new integrator with reset

control block.

Companies are also looking at full digital power

factor correction, although these solutions can have

higher costs associated with them. Fairchild offers an

approach that features a control method based on amodified sinusoidal pulse width modulation.

Fairchilds proposed method does not need to sense

a line current or voltage, and can be implemented by

using one of their low-speed and low-priced conven-

tional microcontrollers.

Power Factor One Inc. uses its patented control

methods including constant pulse proportional cur-

rent, analog reset system, start enforcer and non-

linearity correction to significantly simplify the con-

verters circuit and improve the controllers perform-

ance. The company states that their PF484x PWMcontroller circuits include near-unity PFC circuits

that meet all international standards for electronic


AC PoweringSemiconductor Growth8 byLINNEA BRUSH

Figure 2: TheGPTC110X series

from Green PowerTechnologies controlsPFC stages operating

under continuousconduction mode

conditions

Figure 1: International Rectifiers IR1150 family ofPFC ICs for ac/dc power factor correction circuits



ballast and off-line power conver-

sion applications.

A modular approach for PFC is

provided by Green Power Tech-

nologies Ltd. The company claims

that their plug-and-play products

enable quick and easy integration of

critical components into OEM prod-

ucts with a resulting minimal bill of

materials that reduces costs. The

GPTC110X series is designed to con-

trol the PFC stages operating under

continuous conduction mode condi-

tions. It provides near-unity power factor for a univer-

sal input line (85Vac-265Vac) with no need for sens-

ing the input voltage. GPT is also finalizing develop-

ment of a digital power management module that

incorporates a PFC stage which is expected to be

commercially available within the next year.

A new PFC/PWM controller from ON

Semiconductor with integrated standby and high-

voltage start-up capabilities. The NCP1603 combines

a PFC controller chip and a PWM control chip in a

single, 16-pin SOIC package. Under light load condi-

tions the NCP1603 PWM controller disables the PFCfunction saving in the range of 200mW of power.

Another company looking at digital implementa-

tion is C&D Technologies. They recently presented a

paper at the Digital Power Forum that introduced a

digital/analog power-controlled 5500W rectifier with

three-phase ac input and high power factor. The

topology uses three FET PFC boost

switches and tolerates a wide input

range. Fault detection and control is

monitored by a microprocessor. The

generation of the control reference

for PFC correction is handled both

on an analog level and a micro-

processor level.

Zilker Labs has introduced the

ZL2005, a mixed-signal, power man-

agement and digital PWM IC that

integrates a compact, efficient buck

controller, high-current adaptive

drivers and full power and thermal management

functions in a single package, eliminating the need

for complicated power supply manager chips and

numerous discrete components.

Digital PWM control is also being slowly intro-

duced as a way of enabling high-frequency PWM

converter applications. Texas Instruments introduced

the UCD9501 high resolution DPWM controller

which is part of its Fusion Digital Power family of

products and can achieve up to 150 picoseconds

DPWM resolution.

Silicon Labs debuted the Si8250 DK, a develop-ment kit that includes tools for designing digital power

supply controllers. The kit includes a digital power

supply and PMBus adapter along with software

that the designer uses to describe the desired func-

tions of the controller. The code is synthesized, com-

piled, then put into the chip.

Companies like Roal Electronics are looking at

front-end power supplies with combined digital and

analog control. The company has a single output dig-

ital power front end with a patent-pending multi-

phase digital PFC. A single 8-bit microcontroller isused to manage the PFC, VBULK regulation, alarms

and signal monitoring. An interleaved two-transistor

forward converter PWM control is achieved by using

a standard, low-cost, 10-pin analog IC with direct dig-

ital integration for power management.

Ac powering may not be the primary focus of

many power supply design engineers, but the

demands of distributed power architectures will make

it a challenging area in the next few years. As regu-

lations change, and as digital power moves into the

commercial mainstream, opportunities will emergefor power supply manufacturers to increase efficien-

cy and reduce costs.



Figure 3: ON Semiconductors NCP1603combines a PFC controller chip and aPWM control chip in a single, 16-pin

SOIC package

Figure 4: The Si8250DK is a development kit from Silicon Labs thatincludes tools for designing digital power supply controllers



thesolutionTraditionally, configurable servers have been built

based upon an industry standard rack capable of hold-

ing up to 42, 1U (1.75 inches) servers. Since ac power

is bused through the server rack, each horizontally-mounted 1U server module requires one isolated ac to

dc power supply, or two if redundancy or

load sharing is required, and its own cooling

source. Consequently, a fully-configured 42,

1U rackmount server can house as many as

84 individual power supplies.

Blade servers are mounted vertically

into a 3U rack unit.

Each blade is really

nothing more than a sin-

gle board computer

complete with memory,

processor, and network

connections. By sliding

the blades into a com-

mon vertical enclosure, a larger number of

servers can fit into a smaller allowable spaceresulting in higher computing power density

compared to horizontal rackmount servers.

As many as 250 blades can be installed into

a single PCI based industry standard rack.

Unlike the 1U horizontal rackmount

servers, dc power in a blade server is distrib-

uted from one or more power supply mod-

ules through the PCI cabinet and to each of

the individual blades. Distributing dc power

means that the ac to dc isolation only has to

occur once through an intermediate busconverter. Since the blades themselves do

not have an on-board isolated power supply

or fan, bus power and cooling distribution

can be thought of as shared system resources. Blade

server power supply modules can now be paralleled

and hot-swapped for greater system flexibility and scal-

ability. In their earliest development, blades contained

only a single processor so power dissipation was not a

serious issue. However, the current trend is to pack as

many as four power-hungry processors onto a single

blade which greatly increases cooling demands. And,because the blades themselves are now dissipating so

Scalable Power Systems Meet the Needsof Configurable Blade Servers

8 bySTEVE MAPPUS, TEXAS INSTRUMENTS

CASE Study

thechallengeBlade server computing systems must be highly configurable to

meet a variety of application needs. As a result, blade servers

are bought and sold primarily based upon a desired amount of

processing power required to meet the needs of a specific task.

Ironically, one of the least considered, and yet most important,

components of a blade server is the power supply. After all, it

can be easily argued that a systems reliability is only as good

as the power supplied to it.

Texas Instruments recently worked with a customer wanting

to design a 1.5kW, highly-efficient, isolated power converter

module for a blade server application. This customer relies heav-

ily upon a well-known power module supplier for meeting his

power needs. Power converter modules offer many advantages,

but the foremost must be ease of implementation. However,there are several disadvantages with this approach, particularly

in blade server applications. Server systems are designed to be

highly-configurable in terms of available processing power. To

handle a variety of scalable power requirements, a configurable

server needs to be optimally matched to a compatible power sys-

tem. As a primary obligation, the customer desired more flexibil-

ity by closely matching their power needs and processor require-

ments. Secondly, because of specific supervisory and power

management requirements, the power modules themselves do

not make up a complete power system. And finally, the cus-

tomer emphasized the need to reduce overall power system

costs. Faced with a certain cost increase associated with out-sourcing a custom power converter design for their blade server

applications, this customer boldly decided to do the unthink-

able design his own custom power supply.

CUSTOMERPROFILEA LEADINGMANUFACTUREROF CONFIGURABLEBLADE SERVERCOMPUTINGSYSTEMS



much additional power, there is an ever-increasing

demand to push for higher power supply efficiency.

Because the customer specializes in high-per-

formance computing systems with little to no previous

power supply design experi-

ence, designing an applica-

tion specific, custom power

supply was a significant chal-

lenge. TI worked closely with

the customer to first under-

stand their immediate power

requirements. The 1.5kW

converter needed to operate

from an off-line power factor

correction (PFC) regulated

boost converter. Initially, the

UCC38500 combination

PFC/pulse width modulation

(PWM) controller was con-

sidered, however this ap-

proach was eliminated

because it was limited to sev-

eral hundred watts of power.

A version of the full-bridge

power topology was really theonly practical choice and for

maintaining absolute highest

efficiency the UCC3895

phase shifted full bridge

(PSFB) PWM controller was

chosen along with a

UCC3817 PFC boost pre-

regulator. The PSFB control

technique differs from the

traditional PWM full bridge in

two ways. First, an intention-al delay time is introduced

where, under the right oper-

ating conditions, zero voltage

switching (ZVS) occurs

which would be essential for

meeting the customers need

for high efficiency. Secondly,

the duty cycle of each pri-

mary bridge MOSFET is fixed

at 50 percent, so instead of

the pulse width being controlmodulated it is the phase

shift (or phase overlap) that is controlled. For a compa-

rable component count, the PSFB offers ZVS, EMI and

performance benefits unmatched against the tradition-

al hard-switched full bridge technique.

EDN POWER TECHNOLOGY P19



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Optimizing the converter for high efficiency de-

pends upon a thorough understanding of parasitic cir-

cuit elements, such as MOSFET junction capacitance

and transformer leakage inductance. Even once these

nonlinear elements are defined, the ZVS critical timing

must be precisely adjusted to fully realize the convert-

ers efficiency benefits. Leveraging TIs expertise in ZVS

power topologies, the burden of climbing an otherwise

steep learning curve was

avoided. Throughout the

entire development cycle, TI

provided extensive design

support with specification and

design reviews, component

recommendations and sup-

port of initial hardware

debugging. Within nine

months, the customer had its

first in-house custom

designed power system

ramping into production.

A short time later, this

customer again consulted TI

to discuss their specifications

for a 200W dc to dc convert-

er design. Since favorable

results with the 1.5kW PSFB

design had been achieved,

the customer naturally con-sidered using a scaled-down

200W version. The PSFB

would undoubtedly meet their

requirements of high efficien-

cy and reduced cost, but was

it the best choice? The single-

ended forward converter with

active clamp transformer

reset offers many of the same

advantages found in the

PSFB topology, but at re-duced power levels. Where

the PSFB can be designed to

operate at tens or even hun-

dreds of kilowatts, the active

clamp forward is limited, in a

practical sense, to about

400W. Once the performance

and cost trade-offs were pre-

sented, the customer agreed

to proceed with an active

P20 EDN POWER TECHNOLOGY


P A R T F O U R : E M B E D D ED P O W E R

(Scalable Powercontinued on P33)

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Running OutOf Room?We Suggest

Fewer Chips.Reduce your board size and increaseefficiency with Intersil's multiple outputDC/DC Switching Regulators. Get upto 20A of output current and fourregulated outputs from a single VINranging from 3.3V to 24V.

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4

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ISL6455

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PWMs

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thesolutionA major TV manufacturer asked Fairchild

Semiconductor, to help them design the power supply

system for a 40 digital TV set. The challenge was to

design a power supply system that was small andhighly efficientboth constraints being dictated by

the appliances thin form factor. The power supply

system had to have efficiency

above 85% in normal opera-

tion and meet the Energy Star

requirement of


23/36Enter xx at www.edn.com/infoEnter xx at www.edn.com/infoEDN POWER TECHNOLOGY P23



(24V/8A, 192W) will power the LCD back light invert-

er block, Output 2 (5V/0.5A) will power the logic

block, Output 3 (5V/2A) will power the tuner block

and Output 4 (12V/3A) will power the audio amplifier

block. This adds up to a

total power of 243W in nor-

mal operation with a stand-

by power of less than 1W.

The strategy we adopted

to meet both normal and

stand-by operation was to

divide the entire system into

two sub-systems, a main

power supply sub-system for

normal operation and an auxil-

iary one for stand-by (Figure 2).

Stand-by Operation

In stand-by mode, the main

power is disconnected from

the ac line. We used a relay

and only the stand-by power

supply built around

Fairchilds FSDM311 SMPS

power switch to power thelogic block. The FSDM311

consumes very little power

thanks to its high-voltage

start-up switch and the

advanced burst mode opera-

tion to reduce switching loss.

Normal Operation

In normal operation, the

devices main power supply

was built around FairchildsFAN4800 PFC/PWM mono-

lithic combo controller IC,

which achieves high effi-

ciency using ZVS (zero volt-

age switch) ASHB (asym-

metric half bridge) topology

and utilizes the FAN7382

for high side MOSFET drive.

The patented Leading-Edge

Modulation (LEM) PFC/TEM

Trailing-Edge Modulation(TEM) PWM synchroniza-

tion method reduces ripple

current in the storage capacitor between the PFC and

PWM sections. This results in higher efficiency and

smaller component size. Thanks to these features,

the measured total efficiency at 85Vac was over 85%,

Sometimes looking for the right power supply can be a hassle.Thats why Norvell has developed Power Supply Solutions. This unique

tool will respond to your specifications quickly by accessing severalmanufactures and providing multiple power solutions. Its just thatsimple. Go to norvell.com/pss and experience Norvells newestway to service your needs. Just plug it in, order it and power up!

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24/36Enter xx at www.edn.com/infoEnter xx at www.edn.com/infoP24 EDN POWER TECHNOLOGY NOVEMBER 2005



including the PFC section, and met the customers

demand.

PFC

The FAN4800 meets the PFC regulations thanks to its

high-performance average current mode PFC control

block. As an added bonus, the devices current fed

gain modulator produced excellent noise immunity.

Conclusion

The diffusion of large-sized flat panel television sets is

adding new dimensions to the challenge of power

management and power conservation. Regulatory

agencies have so far focused on power conservation in

stand-by and are just beginning to tackle regulation of

AC LINE

D5SB60

FAN 4800:

LCD

BacklightPS

24V/8A 12V/3A

5V/60mAFSDM311:

Stand-By PS

FAN5234:

DC-DC

5V/2A Tuner

5V/0.5A Logic

FSCQ0765:

Audio PS

Fig. 2. 40 LCD TV Power Supply System

(PFC/PWM continued on P34)

* Output Power from 1 to 10 Watts* Single Outputs to 1000Vdc* Dual Outputs to +/- 500Vdc* 1000Vdc Isolation* Input Ranges (9-36Vdc, 20-60Vdc, 36-72Vdc)* Low Profile Packages (0.8 x 1.25 x 0.52 & 1 x 2 x 0.4)* Typical Efficiency 82%* Pricing starts at $25/1K

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, LTC and LT are registered trademarks and SwitcherCAD is atrademark of Linear Technology Corporation. All other trade-marks are the property of their respective owners.

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Literature: 1-800-4-LINEAR

Support: 408-432-1900

The LTC3780 is Linears latest addition to our growing family of true buck-boost regulators. This wide input voltage range,high power controller is capable of delivering efficiencies of up to 97% for a 12V, 5A output from an input voltage range of4V to 36V. Its current mode topology and single inductor architecture enable simpler solutions than traditional SEPIC ortransformer-based designs. With up to 400kHz operating frequency, compact, high power density designs are easily achieved.

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Info & Online StoreFeatures

VIN Above, Below or Equal to VOUT Single Inductor 4-Switch

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Selectable Low CurrentOperating Modes

200kHz to 400kHz ConstantFrequency Operation,Phase-Lockable

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Datasheet, eval kit with USB

interface, free samples, and

more information available at

www.intersil.com/edn

ISL6299 Key Features:

Dual-Input charger for single-cell Li-ion/

Polymer Batteries for Cradle and USB

Low Component Count

Integrated Pass Element

Fixed 380mA USB Charge Current

Programmable Cradle Charge Current

Charge Current Thermaguard for

Thermal Protection

28V Maximum Voltage for the Cradle Input

Charge and Adapter Presence Indicators

Less than 0.5A Leakage Current off the

Battery when No Input Power Attached

Programmable end-of-charge current with

latch for Cradle Input

No External Blocking Diode Required

Pb-Free Plus Anneal Available

(RoHS Compliant)

Unshackle YourHandheld DeviceFrom Its CradleIntersils ISL6299 is a fully integrated low-cost Li-ionor Li-polymer battery charger that accepts both USBport and desktop cradle charger.


Intersil Battery Charger ICs



Programmable end of charge optimizes

end-customer applications. High input

voltage tolerance protects the device when

used with low cost unregulated supplies or

in under input transient conditions.

Cradle input. The max input voltage tolerance is 28V. Programmablecharge current up to 1A and programmable end of charge current. Theincluded end of charge latch is the default input source.

USB input. Takes input from USB port or other low voltage supply. Fixedcharge current at typically 380mA. Only charges when cradle source isnot connected.

The ISL6299 is a low component count solution that features

programmable cradle charge current, charge indication, adapter

present indication, and programmable end-of-charge (EOC) current

with latch. All these advanced features, along with Intersils Therma-

guard technology for an added measure of thermal protection, are

delivered in this single chip available in a tiny 3x3 mm DFN package.

ISL6299 System

Fast-charging rates of an AC

adaptor for when you have

access to cradle.

Sync-up and fuel-up directly from your

laptop with convenient USB charger.

28V tolerant cradle with

overvoltage protection.
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thesolutionThe concept is illustrated in Figure 2. The isolated

dc/dc Converter is an isolation transformer used to

convert the higher input voltages to a lower interme-

diate bus voltage (IBV), and the efficiency does notappreciably change with the voltage differentials

across the device.

The POLs are not isolated and do not employ a

transformer to convert the IBV to the output voltage,

hence the efficiency of the device varies with the volt-

age differential between the input and the output.

This means that the POL operates more efficiently

with lower voltage differentials across the device.

The printed circuit board (PCB) trace resistances

are constant and the power is a multiple of voltage and

the square of the current (I2R). When delivering power

to a load, it is desirable to raise the distribution voltage

to the highest level feasible so as to lower the current

and minimize the trace voltage drops.

As power requirements in a system

vary, the load currents of each POL, and

thus the total IBV current varies, affect-

ing the PCB trace voltage drops.

At low power requirements the IBV

can be lowered in order to reduce the

voltage drops and increase the efficien-cy of the individual POL converters.

At higher system power require-

ments the IBV can be increased in order to reduce

the PCB current and reduce the trace (I2R) power

losses.

Within a range of varying system power require-

ments, there is an optimum IBV where the efficiency

is maximized.

Analysis calculations, using actual copper cir-

cuit board trace resistances, indicated that even

though the power dissipation in the POLs was higher,at the high required currents, the higher bus voltage

resulted in a slightly better efficiency of 80% for the

12 Volt bus vs. 78% efficiency for the 5 Volt bus.

Which Voltage Bus is Best?8 byLOU PECHI, POWER-ONE, INC.

CASE Study

thechallengeTo meet the design goals of the equipment, the cus-

tomer needed not only to reduce the size of his new

design, but also reduce the material cost while at the

same time increase the functionality of the power con-

version and management functions.

The customer required 8 distinct voltages rangingfrom 0.75 Volts and up to 3.3 Volts at currents rang-

ing from low 3.7 Amp and up to 10 Amp. Besides

sequentially powering each output, in order to assure

proper system operation,

the rate of turn on and

turn off had to be differ-

ent for each output.

To optimize the system

power dissipation the cus-

tomer was faced with the

problem of choosing the

right bus voltage. At low

bus voltages at same over-all power, the current and

the associated I2R dissi-

pation in the circuit board

traces is higher, while at

higher voltages due to the

lower currents the dissipa-

tion is lower. Additionally,

converting higher inputs

to the low outputs at the

point of loads (POLs), the dissipation in the POL itself is

higher. The dissipation in the isolated dc/dc converter

that converts the 48 Volt input to the bus voltage does

not change appreciably due to different isolation trans-former turn ratios, with the output voltage. Thus the

choice of the bus voltage needs to be made based on the

best balance between the circuit board trace and the

POL losses.

CUSTOMERPROFILEA LEADINGDEVELOPER OFNEXT-GENERATIONOPTICAL ULTRA-HIGH-SPEED

TRANSMISSIONTRANSPORTPRODUCTS.

Figure 1. SystemBlock Diagram

Figure 2. Power Dissipation Block Diagram


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29/36Enter xx at www.edn.com/infoEnter xx at www.edn.com/infoEDN POWER TECHNOLOGY P29



Solution Implementation

Simulation of the two intermediate bus voltages con-

firmed the theoretical calculations. The customer

chose the Power-One QBC11ZH-NT isolated con-

verter that met the require-

ments of converting the

wide input worldwide tele-

com bus voltages of 36 to

75Vdc to a 12V bus at 11A.

For the POLs the cus-

tomer had a choice to use

the ZY7007 (7 Amp) and

the ZY7010 (10 Amp) for

the lower currents, and the

ZY7115 (15 Amp) for the

higher output currents.

In order to minimize the

number of different compo-

nents, the customer chose

the ZY7115 intelligent, fullyprogrammable step-down

POL converters, even though

some of the output current

requirements were below the

capabilities of the device.

Besides reducing the num-

ber of different part numbers,

operating way below the

rated output current capabili-

ties of the POLs increased the

overall system reliability.To manage and control

the 8 POLs his choice was

the ZM7108 Digital Power Manager (DPM).

The eight Point of Load Converters (Z-POLs)

were programmed and managed by the eight channel

ZM7108 as shown in Figure 3.

Figure 3. Chosen DPMand Z-POLs

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POWERTOOLS

RoHSCompliant



The DPM bi-directionally communicates with the 8 Z-

One POLs and with the main system through a standard two

wire I2C Bus.

The DPM, besides communicating with the main sys-tem, can set through a graphical user interface (GUI) I 2C

interface each Z-POL converters parameters such as,

output voltage, sequencing, tracking, protection type and

thresholds, frequency, fault propagation, interleave and

feedback loop compensation. The DPM constantly moni-

tors each Z-POL converters output voltage, current and

temperature, while the Z-POLs monitor and report their indi-

vidual status of, over and under voltage protection (OVP &

UVP), and power good high and low (PGH & PGL). Data,

such as output voltage, output current, and temperature, are

constantly updated and stored in the DPMs shift registerand can be accessed in case of system failure. Such teleme-

try data can also be used to monitor the temperature at each

POL location.

Fault management between the Z-POL converters can

be programmed to act differently when faults occur. If no

fault propagation is required, the protection, depending on

fault severity, shuts down just the faulty Z-POL in a latching

or non-latching mode (hiccup with a 130ms period). Fault

propagation within a group of Z-POLs, besides shutting

down the failed Z-POL, shuts down all the Z-POLs within the

group and assures that the group is synchronously turned




Figure 5. Turn on Simulation

Figure 6. 50% Load Transient Simulation

(Which Voltage Bus is Best? continued on P34)

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edn 0504 supplement

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