Texas Instruments' TCA9509 is a highly useful integrated circuit designed for applications such as servers and industrial equipment that require efficient bus repeaters. Specifically, it serves as an I2C bus/SMBus repeater in I2C/SMBus systems.
One of the key features of the TCA9509 is its ability to provide bidirectional voltage-level translation between low voltages (down to 0.9V) and higher voltages (2.7V to 5.5V) in mixed-mode applications. This means that it enables the extension of I2C and similar bus systems without any degradation in performance, even during level shifting.
The TCA9509 device comes equipped with two types of drivers: the A-side drivers and the B-side drivers. Both the inputs and the B-side I/Os are overvoltage tolerant to 5.5V, ensuring robustness and protection against voltage spikes. Additionally, the A-side I/Os are overvoltage tolerant to 5.5V even when the device is unpowered, providing an added layer of safety.
To ensure smooth operation, the TCA9509 incorporates a current-sensing mechanism on the A-side to detect input or output LOW signals, preventing bus lock-up. This mechanism utilizes a 1 mA current source for pull-up and a 200 Ω pull-down driver on the A-side, allowing for smaller voltage swings and reliable signal transmission.
The internal buffer of the A-side is designed to set the output pull-down LOW at approximately 0.2V, while the input threshold of the internal buffer is set about 50 mV lower than the output voltage LOW. This prevents a lock-up condition from occurring when the A-side I/O is driven LOW internally, ensuring smooth communication within the bus.
On the other hand, the B-side drivers are compliant with SMBus I/O levels. The output pull-down on the B-side drives a hard LOW, and the input level is set at 0.3 times the SMBus or I2C-bus voltage level. This enables the B-side to connect seamlessly with other I2C-bus devices or buffers, ensuring compatibility and interoperability.
It's worth noting that the TCA9509 drivers are not enabled unless VCCA is above 0.8V and VCCB is above 2.5V. This ensures that the drivers are only active when the necessary power requirements are met. Furthermore, caution should be exercised when changing the state of the enable (EN) pin, making sure to do so only when the bus is idle to prevent any disruption in communication.
Overall, Texas Instruments' TCA9509 I2C/SMBus bus repeater offers advanced voltage-level translation capabilities, robust drivers, and enhanced compatibility, making it an ideal choice for extending and enhancing I2C and similar bus systems in various applications.
Two-channel bidirectional buffer
I2C Bus and SMBus compatible
Operating supply voltage range: 2.7 V to 5.5 V on the B-side
Operating voltage range: 0.9 V to 5.5 V on the A-side
Voltage-level translation from 0.9 V to 5.5 V and 2.7 V to 5.5 V
Active-high repeater-enable input
Requires no external pullup resistors on lower-voltage port-A
Open-drain I2C I/O
5.5 V tolerant I2C and enable input support mixed-mode signal operation
Lockup-free operation
Accommodates standard-mode and fast-mode I2C devices and multiple masters
Supports arbitration and clock stretching across the repeater
Powered-off high-impedance I2C bus pins
Supports 400 kHz fast I2C Bus operating speeds
Package: 1.6 mm x 1.6 mm, 0.4 mm height, 0.5 mm pitch QFN
Latch-up performance exceeds 100 mA per JESD 78, Class II
ESD protection exceeds JESD 22:
2,000 V human-body model (HBM) (A114-A)
1,000 V charged-device model (C101)
Servers
Routers (telecom switching equipment)
Industrial equipment
Products with many I2C slaves and/or long PCB traces
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