Texas Instruments TCA9802 I2C Manuale utente

SLVUB32–March 2017

TCA9802 I2C Buffer Evaluation Module

User's Guide

SLVUB32–March 2017

TCA9802 I2C Buffer Evaluation Module

The TCA9802EVM evaluation module (EVM) allows the user to connect power to and buffer and translate

I2C commands to the onboard slave device, TMP102. The EVM allows the designer to load and test

different capacitive loading and has the option of replacing a series resistor with an inductor to emulate the

parasitic inductance of cables. Parameters such as rise time, power consumption, and delay times can

easily and accurately be evaluated. For additional details on I2C buffer performance, application notes,

and the data sheet, see www.ti.com/I2C.

Contents

1 Introduction ................................................................................................................... 2

1.1 Overview............................................................................................................. 2

1.2 EVM Features....................................................................................................... 2

2 EVM Hardware Block Diagram and Images.............................................................................. 2

3 Hardware Description ....................................................................................................... 4

4 Layout ......................................................................................................................... 9

4.1 Setup................................................................................................................ 10

5 Operation.................................................................................................................... 11

6 Bill of Materials (BOM)..................................................................................................... 12

List of Figures

1 TCA9802EVM Schematic .................................................................................................. 3

2 TCA9802EVM Top Layout.................................................................................................. 9

3 TCA9802EVM Bottom Layout ............................................................................................. 9

4 Example: USB2ANY I2C Master Connected to the TCA9802EVM .................................................. 10

5 Vias Labeled on the TCA9802EVM...................................................................................... 11

List of Tables

1 Bill of Materials TCA9802EVM ........................................................................................... 12

Trademarks

All trademarks are the property of their respective owners.

Introduction

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TCA9802 I2C Buffer Evaluation Module

1 Introduction

The TCA9802EVM allows designers to evaluate and compare device performance to enable fast selection

of I2C buffers and translators for their system. The TCA9802EVM contains the TCA9802 along with a

linear regulator, TPS71701, and I2C temperature sensors, TMP102. There are other buffers that can be

ordered as samples but are not loaded with the EVM (TCA9800, TCA9801, TCA9803, or TCA9517A).

This allows the designer to evaluate the entire family of devices along with competitor solutions.

1.1 Overview

The TCA9802 is a dual-channel bidirectional buffer intended for I2C bus and SMBus or PMBus systems. It

provides bidirectional level shifting (up-translation and down-translation) between low voltages (down to

0.8 V) and higher voltages (1.65 V to 3.6 V). The TCA9802 features an internal current source on the B-

side of the device, allowing the removal of external pull-up resistors on the B-side. The current source also

provides an improved rise time and ultra-low power consumption.

1.2 EVM Features

This EVM has the following features:

• VCCA input voltage range: 0.8 V to 3.6 V

• VCCB input voltage range: 1.65 V to 3.6 V

• Access to the VCCA, VCCB, OE, SDAA, SCLA, SDAB, and SCLB pins

• Onboard slave device, TMP102, that is programmed using jumpers

• Onboard VCCB regulator, TPS71701, that is programmed using a jumper

• Dual layout to allow for evaluating and comparing competitors or other TCA980x family of devices

• Footprints to test various capacitive loads and series inductance to emulate real-world parasitic affects

2 EVM Hardware Block Diagram and Images

The TCA9802EVM is an evaluation module for the Texas Instruments TCA9802 and TCA980x family of

I2C buffers. It provides basic functionality evaluation for the device. Figure 1 illustrates the EVM schematic.

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EVM Hardware Block Diagram and Images

SLVUB32–March 2017

TCA9802 I2C Buffer Evaluation Module

Figure 1. TCA9802EVM Schematic

J1 is the connector designed to be mated with any I2C master via

0.100" headers. J1 allows for power connection (+VCCA), ground

connection, OE1 for U1, OE2 for U2, SDA, and SCL data lines. U2 is

by default loaded with TCA9802. Connect +VCCA to the EVM using

J1-6.

8TCA9802EVM

Hardware Description

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TCA9802 I2C Buffer Evaluation Module

3 Hardware Description

The TCA9802 EVM is designed to allow the user to easily evaluate the I2C buffer for a variety of

conditions. The breakdown of all the features and design of the EVM follow:

J5 and J6 are the connectors designed to evaluate the B side of the TCA9802.

The J5 and J6 connector on the TCA9802EVM have pins that can be used to

}vvšš}ÆšŒvo^^oÀ_}vvš]}v•(}Œ/2C device. J5 and J6 allows for

connection or the monitoring of SDAB, and SCLB data lines for either U1 or U2

to the onboard temperature sensors U3 and U4 (TMP102).

SCLA SCLA2

SCLA1

SCLA

SDAA

JUMPER

SDAA SDAA2

SDAA1

TCA9802

SCLA

SDAA

SCLB

SDAB

SCLB

SDAB

TMP102

SCL

SDA

TMP102

SCL

SDA

1 2

3 4

5 6

7 8

9 10

The J2 connector allows for either connecting only one device to SDAA or SCLA or to

simultaneously connect to U1 and U2 devices to SDAA and SCLA.

SCLA SCLA2

SCLA1

SCLA

SDAA

JUMPER

SDAA SDAA2

SDAA1

TCA9802

SCLA

SDAA

1 2

3 4

5 6

7 8

9 10

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Hardware Description

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TCA9802 I2C Buffer Evaluation Module

U2 is the device that can be used to compare to the TCA9802, which is in the U1 location.

U2 has the same layout as the U1 location, with the exception that the B side has pull

resistor footprints to allow for comparison with the traditional I2C buffers such as the

TCA9517, which require external pullups. There are also place holders for series resistors

(R27 and R28) and capacitive loads (C13 and C14). R27 and R28 are by default 0-Q

resistors, but can be replaced with chip inductors, if the user wishes to emulate parasitic

inductance. There are two sets of pullup resistors that can be loaded, but the default

configuration is that neither are loaded, thus allowing for immediate testing of other

TCA980x family devices. The two locations allow for testing of systems that have either

the pullups close to U2 or pullups close to the slave device, this assumes that a chip

inductor is loaded to emulate a meaningful amount of inductance.

C15 and C16 are placeholders for capacitive loading of the input waveforms, which by

default are not loaded.

The EVM has also been setup to be able to directly probe onto the SCLB2 and SDAB2.

There are large vias that facilitate the scope probe tips and probe ground connections.

This was designed to minimize the ground loop to minimize noise being picked up by the

probe. This allows for capturing clean waveforms. NOTE: If evaluating a device such as

the TCA9517 at U2, calculate the appropriate pullup resistor and load them on to the

desired pullup resistor location on the B side of the device.

COMPARISON

UNIT

SCLA

SDAA

SCLB

SDAB

TMP102

SCL

SDA

VCCA VCCB

GND

VCCB

0 Ÿ

C14

CLOAD

C13

CLOAD

C15

CLOAD

C16

CLOAD

SCLA2

SDAA2 R23

R24

SCLB2

SDAB2

VCCA

10NŸ

OE2

R27

R28

TEMP2 is the I2C controlled temperature sensor (TMP102) connected to the U2

device. The V+ of the temperature sensor is connected to VOUT of the TPS71701

linear regulator. Its I2C address is 0x49h.

Hardware Description

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TCA9802 I2C Buffer Evaluation Module

The TCA9802 is loaded in the U1 location. The TCA9802 or any of the TCA980x devices do

not need and in fact must not have pullup resistors on the B side of the device. Pullup

resistors will affect the operation of the device. There are also place holders for series

resistors (R25 and R26) and capacitive loads (C7 and C8). R25 and R26 are by default 0-Q

resistors, but can be replaced with chip inductors, if emulating the parasitic inductance of

a wiring harness. C5 and C6 are placeholders for capacitive loading of the input

waveforms, which by default are not loaded.

The EVM has also been setup to be able to directly probe onto the SCLB1 and SDAB1.

There are large vias that facilitate the scope probe tips and probe ground connections.

This was designed to reduce the ground loop to minimize noise being picked up by the

probe. This allows for capturing clean waveforms.

TCA9802

SCLA

SDAA

SCLB

SDAB

TMP102

SCL

SDA

VCCA VCCB

GND

VCCB

0 Ÿ

C14

CLOAD

C13

CLOAD

C15

CLOAD

C16

CLOAD

SCLA2

SDAA2

SCLB2

SDAB2

VCCA

10NŸ

OE2

R27

R28

TEMP1 is the I2C controlled temperature sensor (TMP102) at U3 that is connected

to the U1 device. The V+ of the temperature sensor is connected to VOUT of the

TPS71701 linear regulator. The I2C address of U3 is 0x48h.

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Hardware Description

SLVUB32–March 2017

TCA9802 I2C Buffer Evaluation Module

The TCA9802EVM was designed so that VCCB, the buffered side, can have the input current

measured for comparative analysis. This is generally done with a digital multimeter using

J4 as the connection point. The OE pin for both U1 and U2 can be controlled

independently therefore allowing for comparative analysis between the two. The I2C

temperature sensor, U3 and U4, have their supply on VOUT, therefore not affecting VCCB

current measurements.

TMP102

SCL

SDA

SCL

SDA

VCCA

VCCB

SDAB1

VOUT

VCCA

OE SCLB1

SDAB2

SCLB2

VCCB

OE2

OE1

VCCA

Digital Multimeter:

Current Measurement

TMP102

The TCA9802 EVM has an onboard linear regulator that controls VCCB. VOUT is connected

directly to the V+ supply rail of the TMP102A (U5 and U6), which decouples the current

draw from VCCB. The J4 jumper allows the designer to insert a current meter and measure

the current being consumed by the either U1, U2, or both. VOUT is 3.3 V if there is no

jumper placed on J3. VOUT is 2.5 V if the jumper is placed across J3-5 and J3-6, 1.8 V if the

jumper is placed across J3-3 and J3-4, and 1.65 V if the jumper is placed across J3-1 and

J3-2. NOTE: Place only one jumper on J3 at a time.

TPS71701

Linear

Regulator FB

IN OUT

GND

VOUT

VCCA

R18

49.9NŸ

C19

1 µF

R13

499k

R14

1.05 M R15

332k R16

255k

R20

160k

VCCB

C21

1 µF

+2.5VOUT

+1.8VOUT

+1.65VOUT

OPEN = +3.3VOUT

1 2

3 4

5 6

JUMPER

Hardware Description

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TCA9802 I2C Buffer Evaluation Module

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Layout

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TCA9802 I2C Buffer Evaluation Module

4 Layout

Figure 2 and Figure 3 show the PCB layout images.

Figure 2. TCA9802EVM Top Layout

Figure 3. TCA9802EVM Bottom Layout

Default Jumpers

USB2ANY

357

2468

3 5 7

2 4 6 8

J5 J4 J3 1

SCL SDA

GND+3.3_EXT

TCA9802EVM

Oscilloscope Probe

I2C Master

I2C Slaves

Layout

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TCA9802 I2C Buffer Evaluation Module

4.1 Setup

This section describes the setup and operation of the EVM for evaluation performance. Figure 4 shows

the configuration for operating the TCA9802 I2C buffer using a USB2ANY. An oscilloscope can be

connected directly to J1 or the SDA and SCL pins on J5 and J6. Additional large vias for the SCLB,

SDAB, and ground are placed on the EVM to facilitate oscilloscope probe tips and scope ground

connections. The TCA9802EVM has a dedicated slave peripheral (temperature sensor, TMP102) for each

unit, U1 and U2. The temperature sensor of U1 (U3) has an address of 0x48h and sending an I2C read

command for that address should give you a hex value of approximately 190h, assuming the EVM is at

room temperature (25°C). The address of U4 is 0x49h.

Figure 4. Example: USB2ANY I2C Master Connected to the TCA9802EVM

4.1.1 J1, A Side Connections

This is the connection for the leads from the I2C master source. The signals of the USB2ANY I2C master

are connected as follows: SDAA = J1-1, SCLA = J1-2, GND = J1-3,4,5,7, or 8, and +VCCA= J1-6.

Indice

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