HDMI2C2-14HD Datasheet, PDF (7/31 Pages) STMicroelectronics – ESD protection and signal booster for HDMI™ 1.4 sink interface

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
SDA_IC
VDD_IC
Vtup_IC
V _{Tdown_IC}
t
SDA
5V_IN
70%
30%
T _{FALL_BUS}
T _{RISE_BUS}
IC drives
V_{Tdown_BUS}
Vtup_BUS
VHYST_BUS
t
Cable drives
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.
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