HDMI2C1-14HD Datasheet, PDF (8/32 Pages) STMicroelectronics – HPD pull down and signal conditioning

Application information
HDMI2C1-14HD
Figure 7. Benefit of the dynamic pull-up on the DDC bus
I2C driver without dynamic pull-up
5V_OUT
RPU_BUS
750pF
HDMI™ cable model
IC control
V_{DD_IC}
Signal on the cable
5V_OUT
I2C driver with dynamic pull-up
5V_OUT
logical
circuitry
synchronized
with I2C bus
R_{PU_BUS}
750pF
IC control
V_{DD_IC}
HDMI™ cable model
Signal on the cable
5V_OUT
Rise time out of I2C specification
Risk of communication failure
Rise time compliante with I2C specification
Signal integrity OK even on 750 pF load capacitance
In order to activate the DDC block, the V_{DD_5V} has to reach the specified V_{DD_5V_ON}
threshold (see Table 4). In addition, the inputs and outputs of the bidirectional level shifters
(SCL, SDA, SCL_IC, SDA_IC) must be set to a high level after the power-on, and the HPD
line has to be activated one time.
The DDC outputs (SCL and SDA on cable side) integrate a protection against ESD which is
compliant with IEC61000-4-2 standard, level 4 (8 kV contact).
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