HDMI2C2-14HD Datasheet, PDF (5/31 Pages) STMicroelectronics – ESD protection and signal booster for HDMI™ 1.4 sink interface

HDMI2C2-14HD
2
Application information
Application information
2.1
CEC line description
The CEC bus is described in the HDMI standard as the Consumer Electronics Control. It
provides control functions between all the various audiovisual equipments chained in the
user's environment.
The CEC block integrated in the HDMI2C2-14HD implements a level shifter, shifting the
cable CEC +3.3 V voltage (V_{DD_CEC}) down to the ASIC power supply voltage (V_{DD_IC}) that
can be as low as 1.8 V. The Figure 2 shows the functional diagram of the integrated CEC
block.
VDD_CEC_IC
Figure 2. CEC functional block diagram
VDD_CEC
VDD_CEC_IC
decoupling
capacitance
CEC
driver
CEC_IC
UVLO
Enable
Ctrl
circuit
VDD_CEC
CEC
HDMI
connector
1
3
2
4
5
6
7
8
9
10
11 ₁₂
13
14
15
17
16
18
19
In case of no activity on the CEC bus, or if the CEC driver is off (V_{DD_CEC_IC} = 0), the CEC
pin is put in high impedance mode (open circuit) protecting the circuitry and the application
against hazardous backdrive.
The Figure 3 illustrates the normal operating mode of the CEC functional block when either
the IC from the source on the sink drives the communication.
Figure 3. CEC simplified
CEC_IC
V_{DD_CEC_IC}
V_{IL_CEC_IC}
CEC
V_{DD_CEC}
Block in high
impedance
t_{FALL_CEC}
V_{IH_CEC_IC}
CEC_IC
V_{DD_CEC_IC}
t
t
90%
10%
Level shifting
Source IC drives
CEC
V _{DD_CEC}
t
Block in high
impedance
V _{Tdown_CEC}
Block in high
impedance
V_{HYST_CEC}
Level shifting
V_{Tup_CEC}
t
Block in high
impedance
t_{RISE_CEC}
Sink drives through HDMI cable
DocID024813 Rev1
5/31
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