TMDS442 datasheet(34/47 Pages) TI2

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2C Behavior

Master

Slave

DriverR

Driver T

Rdd

Rup

CABLE

SOURCE

slave

Tdd

Tup

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 I2C Driver

5V_EN(1)

5V_PWR

I2CEN

(1)

X is 1 or 0

The I2CEN pin is active-high with an internal pull-up to VCC. It can be used to isolate a badly behaved slave

during powering up. It should never change state during an I2C operation because disabling during a bus

operation may hang the bus and enabling part way through a bus cycle could confuse the I2C 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 I2C 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

I2C-bus while the slave is connected to a T-side bus. Both buses run at 100 kHz supporting standard-mode I2C

operation. Master devices can be placed on either bus.

Figure 36. Typical Application

Figure 37 illustrates the waveforms seen on the R-side I2C-bus when the master writes to the slave through the

I2C repeater circuit of the TMDS442. This looks like a normal I2C transmission, and the turn on and turn off of the

acknowledge signals are slightly delayed.

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