STHDMI002A

Functional description

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Functional description

The STHDMI002A routes physical layer signals for high bandwidth digital video and is

compatible with low voltage differential signaling standards like TMDS. The device multiplexes

differential outputs from a video source to one of the two corresponding outputs to a common

display. The low on-resistance and low I/O capacitance of STHDMI002A result in a very small

propagation delay. The device integrates SPDT-type switches for 3 differential data TMDS

channels and 1 differential clock channel. Additionally it integrates the switches for DDC and

HPD lines switching.

The I²C interface of the selected input port is linked to the I²C interface of the output port, and

the hot plug detector (HPD) of the selected input port is output to HPD_SINK. For the unused

ports, the I²C interfaces are isolated, and the HPD pins are also isolated.

2.1

HPD pins

The input of the Y_HPD is 5V tolerant, allowing direct connection to 5V signals. The switch is

able to pass both 0V and 5V signal levels. The HPD switch resistance depends on the input

voltage level. At low (near to 0V) input voltage levels, the resistance is 20

Ω typically and at high

(near to 5V) input voltage levels, the resistance is 150

Ω typically.

2.2

DDC channels

The DDC channels are designed with a bi-directional NMOS gate, providing 5V signal

tolerance. The 5V tolerance allows direct connection to a standard I²C bus, thus eliminating the

need for a level shifter. When the input is a 5V, the NMOS switch is turned off and the pull up

resistor on either side of the switch determines the high voltage potential.