USB-to-I2C Isolator and Level Shifter
Contents
1. WAVEFORM A T 2 en TECHANCALSUPPOR vvs KOBLES ROTNG e etere er eC rr ee ee eee rr il 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 INTRODUCTION The Isolator incorporates high speed digital isolators rated at 3 75 kVrms In addition to the voltage isolation level shifting of I2C and SPI signals is possible The USB to I2C hardware operates at 3 3V however using this hardware allows the user to connect 2C and SPI voltages ranging from 2 5V to 5 5V to Master gz owe A gt q i amp a x fi 2 fy f Te stom rea te sr s S we re re s There are two LEDs located on the hardware Each side of the isolator requires a separate supply the LEDs indicate that the voltage sources are applied to the hardware The following bi directional I2C signals are available isolated and level shifted SDA I2C data in and out SCL I2C clock signal The following unidirectional SPI signals are isolated and level shifted SSN Slave Select chip select is an output signal from the isolation hardware MISO Master In Sla2. to I2C Target Systen hardware 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 LEDI 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 The figure to the left shows the layout of the side of the board that is connected to the user s target hardware There are pull ups on the right side of the board These can be removed from the circuit by removing the jumpers at JP3 LED2 illuminates when the right side of the board is powered by the user s hardware I2C Interface Schematic The I2C signals are driven by 74LV07A logic gates The logic gates are powered by the V voltage There are 3 3kOhm pull up resistors to V and 47 Ohm series resistors Use JP3 to remove insert the pull up resistors into the circuit I2C Port Electrical Characteristics Maximum I2C clock SCL Vil Low level input voltage Vih High level output voltage Iol Low level output current Vi Input Voltage Ci Input Capacitance 400 kHz 0 3 V max 0 7 V min 16mA max V 8mA max V 4mA max V 5 5V max 3 0pF ma
3. 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 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 O 2012 SB Solutions Inc All rights reserved Revision 1 0 il Table of Contents INTRODUC THON vvs I2C AND SPI ISOLATOR AND LEVEL SHIFTER CONTENTS ssemrnernnvrnnnrrnnvvnnnvrnnvennnernnuvnnnennnnene GENE STARTED jr MINIMUM REQUIREMENT S sunneste ISOLATOR AND LEVEL SHIFTER SUPPLY VOLTAGE REQUIREMENTS oseese NSTALAION eenen E R HARDWARE DESCRIPTION auvvvvrjevvvavvevmvmvv7vqvvvs O 2C Port Electrical Characteristics vrede SPI Port Electrical CharacterisiliCS EE A ES SP NERO AT rer 2G
4. em m There are no pull ups on the USB to I2C side of the PCB so make sure the pull ups are enabled jumpers inserted on the USB to I2C hardware If all else fails email a description of the problem you are having to us at support i2ctools com Note that all technical support requests must begin with an email to this email address
5. ve Out is an input signal to the isolation hardware MOSI Master Out Slave In is an output signal from the isolation hardware SCLK Master Serial Clock is an output signal from the isolation hardware Note that other IO features and voltage sources available on the USB to I2C hardware are not available on the Isolator hardware I2C AND SPI ISOLATOR AND LEVEL SHIFTER CONTENTS v 2C and SPI Isolation and Level Shifting hardware GETTING STARTED Assumptions We are assuming the user of this product has experience with the I C Bus protocol The I2C Bus specification is a good source of detailed information about the I C Bus The complete specification can be downloaded from the NXP Semiconductors website Static Handling Precautions The I2C and SPI Isolation and Level Shifting hardware contains CMOS devices that can be damaged by ESD It is recommended to use a ground strap or touching the PC case or other grounded source before unpacking or handling the Isolator Hardware MINIMUM REQUIREMENTS v USB to I2C Professional or USB to I2C Elite installed on a Windows PC ISOLATOR AND LEVEL SHIFTER SUPPLY VOLTAGE REQUIREMENTS The I2C Isolator and Level Shifter derives its power on the Master side from the USB to I2C hardware This is a 3 3V supply The target side must be supplied by the target application Do not use a common ground or supply voltages as this will defeat the function of the isolator Each side must use its own suppl
6. x SPI Interface The SPI signals at the target connector are applied to the isolation circuit through 74LV125A logic buffers and 47 ohms series resistors The circuit is shown here 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 Q V 8mA max Q 2mA max Q 16mA max 8mA max Q 2mA max Q 5 5V Notes we have tested the I2C interface up to 800 kHz with no errors but it is guaranteed to operate up to 400 kHz The SPI interface was tested up to 7 5 MHz with no errors but it is guaranteed to operate up to 6 0 MHz This shows a scope trace on a target board operating at 2 5V through the SPI Isolator and Level Shifter Prey Tig tg Noisefilteroff 21 08 37 This shows a scope trace on a target board operating at 2 5V through the I2C Isolator and Level Shifter Tek Ea sr A Data FO Data TT _ m aa Ss eS SS PE oP PE EF Technical Support for the I2C SPI Isolator and Level Shifter is available via an email to m Make sure you have a supply voltage applied to both sides of the isolator hardware The minimum voltage is 2 5V There is an LED on each side of the PCB that should illuminate when properly connected to the USB to I2C hardware and the user target syst
7. y voltage and ground INSTALLATION e The 12C and SPI Isolator and Level Shifter hardware connects directly to the 14 pin ribbon cable from the USB to I2C Professional hardware e Ifusing USB to I2C Elite the 18 pin split cable will require that you connect each individual colored wire to its appropriate connection on the Isolator and Level Shifter hardware e The target side of the hardware requires that you connect a supply voltage equal to the voltage of the I2C SPI hardware you are communicating with e Note that the Isolator and Level Shifter hardware only brings out a subset of the connections from the USB to I2C hardware HARDWARE DESCRIPTION A picture of the isolator is shown below The left side of the board is connected to the USB to I2C hardware The left side is also powered directly by the USB to I2C hardware LED1 on the bottom left side of the board will illuminate when it is connected and powered by the USB to I2C hardware The right side of the board is powered by the user target hardware Power can be applied to either of the V pins on header JP1 The V voltage can be in the range of 2 5V to 5 5V Note that the right side of the board should not be powered from the USB to I2C hardware as this would defeat the isolation properties There are 3 3kOhm pull ups to V on the I2C lines These can be disconnected from the circuit by removing the pull up jumpers Pull up resistor jumpers Connection to User Connection to USB
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