I2C Level Shifter

APPLICATION NOTE

Bi-directional level shifter for I²C-bus and other systems.
AN97055

Philips Semiconductors

Bi-directional level shifter for I²C-bus and other systems.

Application Note AN97055

Abstract

With a single MOS-FET a bi-directional level shifter circuit can be realised to connect devices with different supply voltages of e.g. 5 Volt and 3.3 Volt to one I2C-bussystem. The level shifter can also isolate a bus section of powered-down devices from the I2C-bus, allowing the powered part of the I2C-bus to operate in a normal way. The level shifter can also be used in other bus systems or point to point connections for level shifting and/or isolation.

Purchase of Philips I2C components conveys a license under the I2C patent to use the components in the I2Csystem, provided the system conforms to the I2C specifications defined by Philips.

© Philips Electronics N.V. 1997 All rights are reserved. Reproduction in whole or in part is prohibited without the prior written consent of the copyright owner. The information presented in this document does not form part of any quotation or contract, is believed to be accurate and reliable and may be changedwithout notice. No liability will be accepted by the publisher for any consequence of its use. Publication thereof does not convey nor imply any license under patent- or other industrial or intellectual property rights.

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Philips Semiconductors

Bi-directional level shifter for I²C-bus and other systems.

Application Note AN97055

APPLICATION NOTE

Bi-directional level shifter forI²C-bus and other systems.
AN97055

Author: Herman Schutte Philips Semiconductors Systems Laboratory Eindhoven, The Netherlands

Keywords Level shifter, bi-directional, I²C-bus, gate way, power-off, protection.

Number of pages: 16
Date: 97-08-04

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Philips Semiconductors

Bi-directional level shifter for I²C-bus and other systems.
Summary

Application Note AN97055

Presenttechnologies for integrated circuit with clearances of 0.5 µm and less, limit the maximum supply voltage and consequently the logic levels for the digital I/O signals. To interface these lower voltage circuits with 2 existing 5 Volt devices a level shifter is needed. For bi-directional bus systems as e.g. the I C-bus, such a level shifter must be bi-directional, without the need of a direction controlsignal. With only one appropriate MOS-FET for each bus line the desired level shifting with automatic direction control can be done. The levels may have a vast range, depending on the used MOS-FET, e.g. down to 2 Volt at the “Lower voltage” side and up to 10 Volt or more at the “Higher voltage” side of the level shifter. An additional function of the level shifter is that it can isolate apowered-down section in a bus system, without obstructing the powered part. Another feature is the protection of the “Lower voltage” section against high voltage spikes at the “Higher voltage” section, as long as the MOS-FET can withstand this spikes.

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Philips Semiconductors

Bi-directional level shifter for I²C-bus and other systems.
CONTENTS

Application Note AN97055

1. INTRODUCTION.......................................................................................................................................... 7 1.1 References............................................................................................................................................ 7 1.2 World Wide Web................................................................................................................................... 7 2. INTERCONNECTION OF DEVICES WITH DIFFERENT LOGIC LEVELS. .................................................. 8 2.1 Logic levels of the I C-bus. .................................................................................................................... 8 2.2 I2C-bus devices with different supply voltages and 5V tolerant I/O’s....