HDMI2C2-14HD Datasheet, PDF (6/31 Pages) STMicroelectronics – ESD protection and signal booster for HDMI™ 1.4 sink interface

Application information
HDMI2C2-14HD
In case the application is set in stand-by mode, the +5 V main supply of the application is
generally powered off in order to reduce as much as possible the global power
consumption. The CEC driver can be the only device still working in low power mode,
allowing a wake up of the whole application through the CEC line. When the main power
supply +5 V is switched off, and if the CEC bus is still active (V_{DD_CEC} power in on state),
the HDMI2C2-14HD keeps the CEC bus working properly while all other outputs of the
component are put in high impedance mode.
The CEC output (cable side) integrates a protection against ESD which is compliant with
IEC61000-4-2 standard, level 4 (8kV contact).
2.2
DDC functional block description
The DDC bus is described in the HDMI 1.4 standard as the Display Data Channel. The
topology corresponds to an I2C bus that must be compliant with the I2C bus specification
version 2.1 (January 2000). The DDC bus is made of 2 lines: data line (SDA) and clock line
(SCL). It is used to create a point to point communication link from the source to the sink.
EEDID and HDCP protocols are flowing through this link, making this I2C communication
channel a critical element in the HDMI application.
The DDC block integrated in the HDMI2C2-14HD allows a bidirectional communication
between the cable and the ASIC. It is fully compliant with the HDMI 1.4 standard and its
CTS, but also with the I2C bus specification version 2.1. The DDC block shifts the electrical
and threshold levels of SDA and SCL lines from the +5 V voltage from the cable (V_{5V_IN})
down to the ASIC voltage level (V_{DD_IC}), that can be as low as 1.8 V. The Figure 4 shows
the functional diagram of the DDC block integrated in the HDMI2C2-14HD device.
Figure 4. The DDC functional block diagram (SCL and SDA lines)
VDD_IC
decoupling
capacitance
VDD_IC
HDMI
ASIC
SCL_IC
SDA_IC
+5V
DDC_EN
5V_IN
Enable
reshaping
circuit
Drive
5V_IN
5V_IN
SCL
SDA
1
3
2
5
4
6
7
9
8
10
11 ₁₂
13
14
15
17
16
18
19
HDMI
connector
The DDC_EN allows to authorize or not a bidirectional communication through the
functional block. It can be connected to the main +5V of the board, or to the ASIC power
supply, detecting then if the application is ready for communication or not.
The DDC outputs (SCL and SDA on cable side) integrate a protection against ESD which is
compliant with IEC61000-4-2 standard, level 4 (8kV contact).
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