Texas Instruments TCA9802 I2C User manual

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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.

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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.

www.ti.com EVM Hardware Block Diagram and Images
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TCA9802 I2C Buffer Evaluation Module
Figure 1. TCA9802EVM Schematic

1
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.
5
7
3
4
6
9
1
2
8TCA9802EVM
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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:

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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
U2
SCLA
SDAA
JUMPER
SDAA SDAA2
SDAA1
U1
TCA9802
SCLA
SDAA
SCLB
SDAB
SCLB
SDAB
U4
TMP102
SCL
SDA
U3
TMP102
SCL
SDA
J6
1 2
3 4
5 6
7 8
9 10
4
2
3
1
J5
4
2
3
1
2
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
U2
SCLA
SDAA
JUMPER
SDAA SDAA2
SDAA1
U1
TCA9802
SCLA
SDAA
J2
1 2
3 4
5 6
7 8
9 10
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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.
U2
COMPARISON
UNIT
SCLA
SDAA
SCLB
SDAB
U4
TMP102
SCL
SDA
EN
VCCA VCCB
GND
VCCB
VCCB
VCCB
VCCB
VCCB
0 Ÿ
0 Ÿ
C14
CLOAD
C13
CLOAD
R7
R8
C15
CLOAD
C16
CLOAD
SCLA2
SDAA2 R23
R24
SCLB2
SDAB2
VCCA
10NŸ
OE2
R27
R28
4
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.
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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.
U1
TCA9802
SCLA
SDAA
SCLB
SDAB
U3
TMP102
SCL
SDA
EN
VCCA VCCB
GND
VCCB
0 Ÿ
0 Ÿ
C14
CLOAD
C13
CLOAD
C15
CLOAD
C16
CLOAD
SCLA2
SDAA2
SCLB2
SDAB2
VCCA
10NŸ
OE2
R27
R28
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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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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.
J4
U4
TMP102
SCL
SDA
SCL
SDA
+V
+V
U2
VCCA
OE
VCCB
SDAB1
VOUT
U1
VCCA
OE SCLB1
SDAB2
SCLB2
VCCB
J1
OE2
OE1
VCCA
Digital Multimeter:
Current Measurement
U3
TMP102
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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.
U4
TPS71701
Linear
Regulator FB
EN
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
J4
J3
1 2 3 4 5 6
JUMPER
JUMPER
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TCA9802 I2C Buffer Evaluation Module

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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
1
SCL SDA
GND+3.3_EXT
TCA9802EVM
Oscilloscope Probe
I2C Master
I2C Slaves
2 1
4 3
6 5
8 7
10
9
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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.