I2C and SPI
Isolation and Level
Shifting
Hardware User’s Manual
http://www.i2ctools.com/
Information provided in this document is solely for use with the I2C and SPI Isolator from SB Solutions,
Inc. SB Solutions, Inc. reserves the right to make changes or improvements to this document at any time
without notice. SB Solutions, Inc. assumes no liability whatsoever in the sale or use of this product,
including infringement of any patent or copyright.
Reasonable efforts have been made to ensure the accuracy of the information presented. However, SB
Solutions, Inc. assumes no responsibility for the accuracy of the information.
No part of this document may be reproduced or transmitted in any form or by any means, electronic or
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SB Solutions, Inc.
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Other brand names are trademarks or registered trademarks of their respective owners.
Copyright  2012
SB Solutions, Inc. All rights reserved.
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Revision 1.0
Table of Contents
INTRODUCTION ................................................................................................................... 1 I2C AND SPI ISOLATOR AND LEVEL SHIFTER CONTENTS ..................................................... 1 GETTING STARTED .............................................................................................................. 2 MINIMUM REQUIREMENTS ................................................................................................ 2 ISOLATOR AND LEVEL SHIFTER SUPPLY VOLTAGE REQUIREMENTS ................................... 2 INSTALLATION ..................................................................................................................... 2 HARDWARE DESCRIPTION .................................................................................................. 3 I2C Port Electrical Characteristics ................................................................................................ 5 SPI Port Electrical Characteristics ................................................................................................ 5 SPI WAVEFORM AT 2.5V ..................................................................................................... 6 I2C WAVEFORM AT 2.5V ..................................................................................................... 6 TECHNICAL SUPPORT .......................................................................................................... 6 TROUBLESHOOTING ............................................................................................................ 6 iii
DISCLAIMER AND WARRANTY
Proper use of I2C and SPI Isolator and level shifter is the sole responsibility of the user.
SB Solutions, Inc. is not responsible for any damage resulting from misuse or improper
installation.
SB Solutions, Inc. will, at our option, repair or replace a defective I2C and SPI Isolator
and Level Shifter hardware within thirty (30) days of the purchase date. Return shipping
is the responsibility of the user.
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INTRODUCTION TheIsolatorincorporateshigh‐speeddigitalisolatorsratedat3.75kVRMS.In
additiontothevoltageisolation,levelshiftingofI2CandSPIsignalsispossible.The
USB‐to‐I2Chardwareoperatesat3.3V,however,usingthishardware,allowsthe
usertoconnectI2CandSPIvoltagesrangingfrom2.5Vto5.5V.
TherearetwoLEDslocatedonthehardware.Eachsideoftheisolatorrequiresa
separatesupply;theLEDsindicatethatthevoltagesourcesareappliedtothe
hardware.
Thefollowingbi‐directionalI2Csignalsareavailableisolatedandlevelshifted:
SDA–I2Cdatainandout
SCL–I2Cclocksignal
ThefollowingunidirectionalSPIsignalsareisolatedandlevelshifted:
SSN–SlaveSelect(chipselect)–isanoutputsignalfromtheisolationhardware
MISO–MasterIn;SlaveOut–isaninputsignaltotheisolationhardware
MOSI–MasterOut;SlaveIn–isanoutputsignalfromtheisolationhardware
SCLK–MasterSerialClock–isanoutputsignalfromtheisolationhardware
NotethatotherIOfeaturesandvoltagesourcesavailableontheUSB‐to‐I2C
hardwarearenotavailableontheIsolatorhardware.
I2C AND SPI ISOLATOR AND LEVEL SHIFTER CONTENTS  I2CandSPIIsolationandLevelShiftinghardware
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GETTING STARTED Assumptions
WeareassumingtheuserofthisproducthasexperiencewiththeI²CBusprotocol.
TheI2CBusspecificationisagoodsourceofdetailedinformationabouttheI2CBus.
ThecompletespecificationcanbedownloadedfromtheNXPSemiconductors
website.
StaticHandlingPrecautions
TheI2CandSPIIsolationandLevelShiftinghardwarecontainsCMOSdevicesthat
canbedamagedbyESD.Itisrecommendedtouseagroundstraportouchingthe
PCcaseorothergroundedsourcebeforeunpackingorhandlingtheIsolator
Hardware.
MINIMUM REQUIREMENTS  USB‐to‐I2CProfessionalorUSB‐to‐I2CEliteinstalledonaWindowsPC
ISOLATOR AND LEVEL SHIFTER SUPPLY VOLTAGE REQUIREMENTS TheI2CIsolatorandLevelShifterderivesitspowerontheMastersidefromthe
USB‐to‐I2Chardware.Thisisa3.3Vsupply.
Thetargetsidemustbesuppliedbythetargetapplication.Donotuseacommon
groundorsupplyvoltagesasthiswilldefeatthefunctionoftheisolator.Eachside
mustuseitsownsupplyvoltageandground.
INSTALLATION 



TheI2CandSPIIsolatorandLevelShifterhardwareconnectsdirectlytothe14‐
pinribboncablefromtheUSB‐to‐I2CProfessionalhardware.
IfusingUSB‐to‐I2CElite,the18‐pinsplitcablewillrequirethatyouconnecteach
individualcoloredwiretoitsappropriateconnectionontheIsolatorandLevel
Shifterhardware
Thetargetsideofthehardwarerequiresthatyouconnectasupplyvoltageequal
tothevoltageoftheI2C/SPIhardwareyouarecommunicatingwith
NotethattheIsolatorandLevelShifterhardwareonlybringsoutasubsetofthe
connectionsfromtheUSB‐to‐I2Chardware
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HARDWARE DESCRIPTION Apictureoftheisolatorisshownbelow.TheleftsideoftheboardisconnectedtotheUSB‐to‐I2Chardware.
TheleftsideisalsopowereddirectlybytheUSB‐to‐I2Chardware.LED1onthebottomleftsideoftheboard
willilluminatewhenitisconnectedandpoweredbytheUSB‐to‐I2Chardware.
Therightsideoftheboardispoweredbytheusertargethardware.PowercanbeappliedtoeitheroftheV+
pinsonheaderJP1.TheV+voltagecanbeintherangeof2.5Vto5.5V.Notethattherightsideoftheboard
shouldnotbepoweredfromtheUSB‐to‐I2Chardware,asthiswoulddefeattheisolationproperties.
Thereare3.3kOhmpull‐upstoV+ontheI2Clines.Thesecanbedisconnectedfromthecircuitbyremoving
thepull‐upjumpers.
The figure to the left shows the layout of the side of the
board that is connected to the USB-to-I2C hardware.
There are no pull-ups on the left side of the board, so the
pull-up jumpers on the USB-to-I2C hardware should be
used.
LED1 illuminates when the left side of the board is powered
by the USB-to-I2C hardware.
The signals from the USB-to-I2C hardware are limited to the
following SPI signals: SSN (or Chip Select), MISO, MOSI,
and SCLK; as well as the following I2C signals: SCL (serial
clock) and SDA (serial data).
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Thefiguretotheleftshowsthelayoutof
thesideoftheboardthatisconnectedto
theuser’stargethardware.
Therearepull‐upsontherightsideofthe
board.Thesecanberemovedfromthe
circuitbyremovingthejumpersatJP3.
LED2illuminateswhentherightsideof
theboardispoweredbytheuser’s
hardware.
I2CInterfaceSchematic
TheI2Csignalsaredrivenby74LV07Alogicgates.
ThelogicgatesarepoweredbytheV+voltage.
Thereare3.3kOhmpull‐upresistorstoV+,and47
Ohmseriesresistors.UseJP3toremove/insert
thepull‐upresistorsintothecircuit.
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SPIInterface
TheSPIsignalsatthe
targetconnectorare
appliedtotheisolation
circuitthrough
74LV125Alogicbuffers
and47ohmsseries
resistors.Thecircuitis
shownhere.
I2C Port Electrical Characteristics
Maximum I2C clock (SCL):
Vil Low level input voltage:
Vih High level output voltage:
Iol Low level output current:
Vi
Ci
Input Voltage
Input Capacitance
400 kHz
0.3*V+ (max)
0.7*V+ (min)
16mA max @ V+ =4.5-5.5V
8mA max @ V+ =3.0-3.6V
4mA max @ V+ =2.5-2.7V
5.5V max
3.0pF max
SPI Port Electrical Characteristics
Maximum Serial Clock (SCLK):
Vil Low level input voltage:
Vih High level output voltage:
Iol Low level output current:
Ioh High level output current:
Vi
Input Voltage
6.0 MHz
0.3*V+ (max)
0.7*V+ (min)
16mA max @ V+
8mA max @ V+
2mA max @ V+
-16mA max@ V+
-8mA max @ V+
-2mA max @ V+
5.5V
=4.5-5.5V
=3.0-3.6V
=2.5-2.7V
=4.5-5.5V
=3.0-3.6V
=2.5-2.7V
Notes:wehavetestedtheI2Cinterfaceupto800kHzwithnoerrors,butitisguaranteedto
operateupto400kHz.
TheSPIinterfacewastestedupto7.5MHzwithnoerrors,butitisguaranteedtooperate
upto6.0MHz.
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SPI WAVEFORM AT 2.5V Thisshowsascopetraceonatargetboardoperatingat2.5VthroughtheSPIIsolatorand
LevelShifter.
I2C WAVEFORM AT 2.5V Thisshowsascopetraceonatargetboardoperatingat2.5VthroughtheI2CIsolatorand
LevelShifter.
TECHNICAL SUPPORT TechnicalSupportfortheI2C/SPIIsolatorandLevelShifterisavailableviaanemailto
support@i2ctools.com.
TROUBLESHOOTING 
Makesureyouhaveasupplyvoltageappliedtobothsidesoftheisolatorhardware.
Theminimumvoltageis2.5V.ThereisanLEDoneachsideofthePCBthatshould
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
illuminatewhenproperlyconnectedtotheUSB‐to‐I2Chardwareandtheusertarget
system.
Therearenopull‐upsontheUSB‐to‐I2CsideofthePCB,somakesurethepull‐upsare
enabled(jumpersinserted)ontheUSB‐to‐I2Chardware.
Ifallelsefails,emailadescriptionoftheproblemyouarehavingtousat
support@i2ctools.com.
Notethatalltechnicalsupportrequestsmustbeginwithanemailtothisemailaddress.
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