Datasheet

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I
2
C Behavior
Master
Slave
DriverR
Driver T
V
Rdd
R
Rup
C
CABLE
C
SOURCE
C
I
C
O
C
slave
V
Tdd
R
Tup
C
medium
TMDS442
SLLS757A – AUGUST 2006 – REVISED MARCH 2007
When GE sets high, or GE sets low and 5V_EN sets high, the EN signal is the AND result of the 5V_PWR and
the I2CEN. When GE sets low and 5V_EN sets low, the EN signals follows the status of I2CEN. See Table 5 .
Table 5. Truth Table for the EN Signal of the I
2
C Driver
GE 5V_EN
(1)
5V_PWR I2CEN EN
1 X 1 1 1
1 X 1 0 0
1 X 0 1 0
1 X 0 0 0
0 1 1 1 1
0 1 1 0 0
0 1 0 1 0
0 1 0 0 0
0 0 1 1 1
0 0 1 0 0
0 0 0 1 1
0 0 0 0 0
(1) X is 1 or 0
The I2CEN pin is active-high with an internal pull-up to V
CC
. It can be used to isolate a badly behaved slave
during powering up. It should never change state during an I
2
C operation because disabling during a bus
operation may hang the bus and enabling part way through a bus cycle could confuse the I
2
C parts being
enabled.
The typical application of the TMDS442 is as a repeater in a TV connecting the HDMI input connector and an
internal HDMI Rx through flat cables. The I
2
C repeater is 5-V tolerant, and no additional circuitry is required to
translate between 3.3-V to 5-V bus voltages. In the following example, the system master is running on an R-side
I
2
C-bus while the slave is connected to a T-side bus. Both buses run at 100 kHz supporting standard-mode I
2
C
operation. Master devices can be placed on either bus.
Figure 36. Typical Application
Figure 37 illustrates the waveforms seen on the R-side I
2
C-bus when the master writes to the slave through the
I
2
C repeater circuit of the TMDS442. This looks like a normal I
2
C transmission, and the turn on and turn off of the
acknowledge signals are slightly delayed.
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