This TCA9509RVHR integrated circuit is an I2C bus/SMBus Repeaterfor use in I2C/SMBus systems. It can also provide bidirectionalvoltage-level translation (up-translation/down-translation) between low voltages (down to 0.9 V)and higher voltages (2.7 V to 5.5 V) in mixed-mode applications. This device enablesI2C and similar bus systems to be extended, without degradation ofperformance even during level shifting.

The TCA9509RVHR buffers both the serial data (SDA) and the serial clock (SCL) signals on theI2C bus, thus allowing 400-pF bus capacitance on the B-side. This devicecan also be used to isolate two halves of a bus for voltage and capacitance.

The TCA9509RVHR has two types of drivers – A-side drivers and B-side drivers. All inputs andB-side I/Os are overvoltage tolerant to 5.5 V. The A-side I/Os are overvoltage tolerant to 5.5 Vwhen the device is unpowered (VCCB and/or VCCA = 0 V).

The bus port B drivers are compliant with SMBus I/O levels, while the A-side uses acurrent sensing mechanism to detect the input or output LOW signal which prevents bus lock-up. TheA-side uses a 1 mA current source for pull-up and a 200 Ω pull-down driver. This results in a LOWon the A-side accommodating smaller voltage swings. The output pull-down on the A-side internalbuffer LOW is set for approximately 0.2 V, while the input threshold of the internal buffer is setabout 50 mV lower than that of the output voltage LOW. When the A-side I/O is driven LOWinternally, the LOW is not recognized as a LOW by the input. This prevents a lock-up condition fromoccurring. The output pull-down on the B-side drives a hard LOW and the input level is set at 0.3of SMBus or I2C-bus voltage level which enables B side to connect to anyother I2C-bus devices or buffer.

The TCA9509RVHR drivers are not enabled unless VCCA is above 0.8 V andVCCB is above 2.5 V. The enable (EN) pin can also be used to turn thedrivers on and off under system control. Caution should be observed to only change the state of theEN pin when the bus is idle.

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