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FXMAR2102 Datasheet, PDF (8/16 Pages) Fairchild Semiconductor – Dual-Supply, 2-Bit Voltage Translator / Isolator for I2C Applications | |||
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I2C Bus Isolation
The FXMAR2102 supports I2C-Bus® isolation for the
following conditions:
ï§ Bus isolation if bus clear
ï§ Bus isolation if either VCC goes to ground
Bus Clear
Because the I2C specification defines the minimum SCL
frequency of DC, the SCL signal can be held LOW
forever; however. This condition shuts down the I2C bus.
The I2C specification refers to this condition as âBus
Clear.â In Figure 7; if slave #2 holds down SCL forever,
the master and slave #1 are not able to communicate
because the FXMAR2102 passes the SCL stuck-LOW
condition from slave #2 to slave #1 and as the master.
However, if the OE pin is pulled LOW (disabled), both
ports (A and B) are 3-stated. This results in the
FXMAR2102 isolating slave #2 from the master and
slave #1, allowing full communication between the
master and slave #1.
VCC to GND
If slave #2 is a camera that is suddenly removed from
the I2C bus, resulting in VCCB transitioning from a valid
VCC (1.65V â 5.5V) to 0V; the FXMAR2102
automatically forces SCL and SDA on both its A and B
ports into 3-state. Once VCCB has reached 0V, full I2C
communication between the master and slave #1
remains undisturbed.
Figure 7. Bus Isolation
© 2011 Fairchild Semiconductor Corporation
FXMAR2102 ⢠Rev. 1.0.0
8
www.fairchildsemi.com
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