TCA9509 Datasheet, PDF (2/14 Pages) Texas Instruments – LEVEL-TRANSLATING I2C/SMBUS BUS REPEATER

TCA9509
SCPS225 – JUNE 2011
www.ti.com
DESCRIPTION/ORDERING INFORMATION (CONTINUED)
The bus port B drivers are compliant with SMBus I/O levels, while the A side uses a current sensing mechanism
to detect the input or output LOW signal which prevents bus lock-up. The A side uses a 1 mA current source for
pull-up and a 200 Ω pull-down driver. This results in a LOW on the A side accommodating smaller voltage
swings. The output pull-down on the A side internal buffer LOW is set for approximately 0.2 V, while the input
threshold of the internal buffer is set about 50 mV lower than that of the output voltage LOW. When the A side
I/O is driven LOW internally, the LOW is not recognized as a LOW by the input. This prevents a lock-up condition
from occurring. The output pull-down on the B side drives a hard LOW and the input level is set at 0.3 of SMBus
or I²C-bus voltage level which enables B side to connect to any other I²C-bus devices or buffer.
The TCA9509 drivers are not enabled unless V_CCA is above 0.8 V and V_CCB is above 2.5 V. The enable (EN) pin
can also be used to turn the drivers on and off under system control. Caution should be observed to only change
the state of the EN pin when the bus is idle.
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