HDMI2C2-14HD datasheet(7/31 Pages) STMICROELECTRONICS

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DocID024813 Rev1

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HDMI2C2-14HD

Application information

The Figure 5 illustrates the electrical parameters of the DDC block specified in Table 7.

Figure 5. Simplified view of the electrical parameters of the DDC functional block

The HDMI standard specifies that the maximum capacitance of the cable can be as high as

700 pF. Knowing that the maximum capacitance of the source input can reach up to 50 pF,

this means that the I2C driver must be able to drive a load capacitance up to 750pF. On the

other hand, the I2C standard specifies that the maximum rise time of the signal must be

lower than 1 µs in order to keep the signal integrity. Taking into account the maximum cable

capacitance of 750 pF, it is not possible to guarantee a rise time lower than 1 µs in worst

case. Therefore, a dynamic pull-up, synchronized with the I2C driver, has been integrated at

the output of SDA and SCL lines. This signal booster accelerates for a short period the

charging time of the equivalent cable capacitance, allowing to drive any HDMI cable. This

dynamic pull-up is recommended by the I2C standard. The Figure 6 illustrates the benefit of

the dynamic pull-up integrated in the HDMI2C2-14HD device.

5V_IN

SDA

VDD_IC

SDA_IC

V Tdown_IC

TRISE_BUS

Vtup_IC

70%

30%

Tdown_BUS

Vtup_BUS

VHYST_BUS

IC drives

Cable drives

FALL_BUS

HDMI2C2-14HD Datasheet(PDF) 7 Page - STMicroelectronics