HDMI2C1-6C1 Datasheet, PDF (4/23 Pages) STMicroelectronics – ESD protection and signal booster for HDMI source control stage interface

Application information
2
Application information
HDMI2C1-6C1
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 equipment chained in the
user's environment.
The CEC block integrated in the HDMI2C1-6C1 implements a level shifter, shifting the cable
CEC line from +3.3 V CEC 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.
Figure 2. CEC link functional block diagram
VDD_CEC_IC
VDD_CEC
VDD_CEC_IC
decoupling
capacitance
CEC
driver
CEC_IC
UVLO
Enable
Ctrl
circuit
VDD_CEC
CEC
HDMI
connector
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
In case of no activity on the CEC bus, or if the CEC driver is off (V_{DD_CEC} = 0), the output
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 or 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}
90%
10%
Level shifting
Source IC drives
CEC_IC
V_{DD_CEC_IC}
t
t
CEC
V_{DD_CEC}
V_{Tdown_CEC}
V_{HYST_CEC}
V_{Tup_CEC}
t
Block in high
impedance
t _{RISE_CEC}
t
Block in high
impedance
Level shifting
Block in high
impedance
Sink drives through HDMI cable
4/23
DocID025281 Rev 1