I2C and SPI Isolation and Level

Shifting

Hardware User’s Manual

http://www.i2ctools.com/

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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 mechanical, for any purpose, without the express written permission of SB Solutions, Inc. P.O. Box 4506 Cary, NC 27519-4506 Other brand names are trademarks or registered trademarks of their respective owners. Copyright 2012 SB Solutions, Inc. All rights reserved. Revision 1.0

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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     

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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.Inadditiontothevoltageisolation,levelshiftingofI2CandSPIsignalsispossible.TheUSB‐to‐I2Chardwareoperatesat3.3V,however,usingthishardware,allowstheusertoconnectI2CandSPIvoltagesrangingfrom2.5Vto5.5V.

TherearetwoLEDslocatedonthehardware.Eachsideoftheisolatorrequiresaseparatesupply;theLEDsindicatethatthevoltagesourcesareappliedtothehardware.Thefollowingbi‐directionalI2Csignalsareavailableisolatedandlevelshifted:SDA–I2CdatainandoutSCL–I2CclocksignalThefollowingunidirectionalSPIsignalsareisolatedandlevelshifted:SSN–SlaveSelect(chipselect)–isanoutputsignalfromtheisolationhardwareMISO–MasterIn;SlaveOut–isaninputsignaltotheisolationhardwareMOSI–MasterOut;SlaveIn–isanoutputsignalfromtheisolationhardwareSCLK–MasterSerialClock–isanoutputsignalfromtheisolationhardwareNotethatotherIOfeaturesandvoltagesourcesavailableontheUSB‐to‐I2ChardwarearenotavailableontheIsolatorhardware.

I2C AND SPI ISOLATOR AND LEVEL SHIFTER CONTENTS 

I2CandSPIIsolationandLevelShiftinghardware

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GETTING STARTED  AssumptionsWeareassumingtheuserofthisproducthasexperiencewiththeI²CBusprotocol.TheI2CBusspecificationisagoodsourceofdetailedinformationabouttheI2CBus.ThecompletespecificationcanbedownloadedfromtheNXPSemiconductorswebsite.StaticHandlingPrecautionsTheI2CandSPIIsolationandLevelShiftinghardwarecontainsCMOSdevicesthatcanbedamagedbyESD.ItisrecommendedtouseagroundstraportouchingthePCcaseorothergroundedsourcebeforeunpackingorhandlingtheIsolatorHardware.

MINIMUM REQUIREMENTS  USB‐to‐I2CProfessionalorUSB‐to‐I2CEliteinstalledonaWindowsPC

 ISOLATOR AND LEVEL SHIFTER SUPPLY VOLTAGE REQUIREMENTS 

TheI2CIsolatorandLevelShifterderivesitspowerontheMastersidefromtheUSB‐to‐I2Chardware.Thisisa3.3Vsupply.Thetargetsidemustbesuppliedbythetargetapplication.Donotuseacommongroundorsupplyvoltagesasthiswilldefeatthefunctionoftheisolator.Eachsidemustuseitsownsupplyvoltageandground.

INSTALLATION 

TheI2CandSPIIsolatorandLevelShifterhardwareconnectsdirectlytothe14‐pinribboncablefromtheUSB‐to‐I2CProfessionalhardware.

IfusingUSB‐to‐I2CElite,the18‐pinsplitcablewillrequirethatyouconnecteachindividualcoloredwiretoitsappropriateconnectionontheIsolatorandLevelShifterhardware

ThetargetsideofthehardwarerequiresthatyouconnectasupplyvoltageequaltothevoltageoftheI2C/SPIhardwareyouarecommunicatingwith

NotethattheIsolatorandLevelShifterhardwareonlybringsoutasubsetoftheconnectionsfromtheUSB‐to‐I2Chardware

 

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HARDWARE DESCRIPTION Apictureoftheisolatorisshownbelow.TheleftsideoftheboardisconnectedtotheUSB‐to‐I2Chardware.TheleftsideisalsopowereddirectlybytheUSB‐to‐I2Chardware.LED1onthebottomleftsideoftheboardwillilluminatewhenitisconnectedandpoweredbytheUSB‐to‐I2Chardware.Therightsideoftheboardispoweredbytheusertargethardware.PowercanbeappliedtoeitheroftheV+pinsonheaderJP1.TheV+voltagecanbeintherangeof2.5Vto5.5V.NotethattherightsideoftheboardshouldnotbepoweredfromtheUSB‐to‐I2Chardware,asthiswoulddefeattheisolationproperties.Thereare3.3kOhmpull‐upstoV+ontheI2Clines.Thesecanbedisconnectedfromthecircuitbyremovingthepull‐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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Thefiguretotheleftshowsthelayoutofthesideoftheboardthatisconnectedtotheuser’stargethardware.Therearepull‐upsontherightsideoftheboard.ThesecanberemovedfromthecircuitbyremovingthejumpersatJP3.LED2illuminateswhentherightsideoftheboardispoweredbytheuser’shardware.

I2CInterfaceSchematicTheI2Csignalsaredrivenby74LV07Alogicgates.ThelogicgatesarepoweredbytheV+voltage.Thereare3.3kOhmpull‐upresistorstoV+,and47Ohmseriesresistors.UseJP3toremove/insertthepull‐upresistorsintothecircuit.

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SPIInterfaceTheSPIsignalsatthetargetconnectorareappliedtotheisolationcircuitthrough74LV125Alogicbuffersand47ohmsseriesresistors.Thecircuitisshownhere.  

I2C Port Electrical Characteristics

Maximum I2C clock (SCL): 400 kHz Vil Low level input voltage: 0.3*V+ (max) Vih High level output voltage: 0.7*V+ (min) Iol Low level output current: 16mA max @ V+ =4.5-5.5V 8mA max @ V+ =3.0-3.6V 4mA max @ V+ =2.5-2.7V Vi Input Voltage 5.5V max Ci Input Capacitance 3.0pF max

SPI Port Electrical Characteristics

Maximum Serial Clock (SCLK): 6.0 MHz Vil Low level input voltage: 0.3*V+ (max) Vih High level output voltage: 0.7*V+ (min) Iol Low level output current: 16mA max @ V+ =4.5-5.5V 8mA max @ V+ =3.0-3.6V 2mA max @ V+ =2.5-2.7V Ioh High level output current: -16mA max@ V+ =4.5-5.5V -8mA max @ V+ =3.0-3.6V -2mA max @ V+ =2.5-2.7V Vi Input Voltage 5.5V

Notes:wehavetestedtheI2Cinterfaceupto800kHzwithnoerrors,butitisguaranteedtooperateupto400kHz.TheSPIinterfacewastestedupto7.5MHzwithnoerrors,butitisguaranteedtooperateupto6.0MHz.

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SPI WAVEFORM AT 2.5V Thisshowsascopetraceonatargetboardoperatingat2.5VthroughtheSPIIsolatorandLevelShifter.

 I2C WAVEFORM AT 2.5V Thisshowsascopetraceonatargetboardoperatingat2.5VthroughtheI2CIsolatorandLevelShifter.

TECHNICAL SUPPORT 

TechnicalSupportfortheI2C/SPIIsolatorandLevelShifterisavailableviaanemailtosupport@i2ctools.com.

TROUBLESHOOTING 

Makesureyouhaveasupplyvoltageappliedtobothsidesoftheisolatorhardware.

Theminimumvoltageis2.5V.ThereisanLEDoneachsideofthePCBthatshould

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illuminatewhenproperlyconnectedtotheUSB‐to‐I2Chardwareandtheusertargetsystem.

Therearenopull‐upsontheUSB‐to‐I2CsideofthePCB,somakesurethepull‐upsareenabled(jumpersinserted)ontheUSB‐to‐I2Chardware.

Ifallelsefails,emailadescriptionoftheproblemyouarehavingtousatsupport@i2ctools.com.Notethatalltechnicalsupportrequestsmustbeginwithanemailtothisemailaddress.