1 Features
• Two-Channel Bidirectional Buffer
• I2C Bus and SMBus Compatible
• Operating Supply Voltage Range of 0.9V to 5.5V
on A-side
• Operating Supply Voltage Range of 2.7V to 5.5V
on B-side
• Voltage-Level Translation From 0.9V - 5.5V to
2.7V - 5.5V
• Footprint and Functional Replacement for
PCA9515B
• Active-High Repeater-Enable Input
• Open-Drain I2C I/O
• 5.5V Tolerant I2C and Enable Input Support Mixed-
Mode Signal Operation
• Accommodates Standard Mode and Fast Mode
I2C Devices and Multiple Masters
• High-Impedance I2C Pins When Powered-Off
• Latch-Up Performance Exceeds 100mA Per JESD
78, Class II
• ESD Protection Exceeds JESD 22
– 5500V Human-Body Model (A114-A)
– 200V Machine Model (A115-A)
– 1000V Charged-Device Model (C101)

2 Applications
• Servers
• Routers (Telecom Switching Equipment)
• Industrial Equipment
• Products with Many I2C Slaves and/or Long PCB
Traces

3 Description
The TCA9517A is a bidirectional buffer with level
shifting capabilities for I2C and SMBus systems.
It provides bidirectional voltage-level translation (uptranslation/
down-translation) between low voltages
(down to 0.9V) and higher voltages (2.7V to 5.5V)
in mixed-mode applications. This device enables
I2C and SMBus systems to be extended without
degradation of performance, even during level
shifting.
The TCA9517A buffers both the serial data (SDA) and
the serial clock (SCL) signals on the I2C bus, thus
allowing two buses of up to 400pF bus capacitance to
be connected in an I2C application.
The TCA9517A has two types of drivers: A-side
drivers and B-side drivers. All inputs and I/Os are
over-voltage tolerant to 5.5V, even when the device
is unpowered (VCCB and/or VCCA = 0V).
The TCA9517A offers a higher contention level
threshold, VILC, than the TCA9517, which allows
connections to slaves which have weaker pulldown
ability.
The type of buffer design on the B-side prevents it
from being used in series with devices which use
static voltage offset. This is because these devices
do not recognize buffered low signals as a valid low
and do not propagate it as a buffered low again.
The B-side drivers operate from 2.7 V to 5.5 V.
The output low level for this internal buffer is
approximately 0.5 V, but the input voltage must be
70 mV or more below the output low level when the
output internally is driven low. The higher-voltage low
signal is called a buffered low. When the B-side I/O
is driven low internally, the low is not recognized as
a low by the input. This feature prevents a lockup
condition from occurring when the input low condition
is released.