STDEV003ABTR datasheet(10/41 Pages) STMICROELECTRONICS

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Functional description

STDVE003A

10/41

Functional description

The STDVE003A routes physical layer signals for high bandwidth digital video and is

compatible with low voltage differential signaling standard like TMDS. The device passes the

differential inputs from a video source to a common display when it is in the active mode of

operation. The device conforms to the TMDS standard on both inputs and outputs.

The low on-resistance and low I/O capacitance of the switch in STDVE003A 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 line switching with I2C repeater on the DDC lines.

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 driven to L state.

3.1

Adaptive equalizer

The equalizer dramatically reduces the intersymbol interference (ISI) jitter and attenuation

from long or lossy transmission media. The inputs present high impedance when the device

is not active or when VCC is absent or 0 V. In all other cases, the 50 Ω termination resistors

on input channels are present.

This circuit helps to improve the signal eye pattern significantly. Shaping is performed by the

gain stage of the equalizer to compensate the signal degradation and then the signals are

driven on to the output ports.

The equalizer is fully adaptive and automatic in function providing smaller gain at low

frequencies and higher gain at high frequencies. The default setting of EQ_BOOST = L is

recommended for optimized operation.

Table 3.

Gain frequency response

Frequency

(MHz)

Gain in dB

(EQ_BOOST = 0)

Gain in dB

(EQ_BOOST = 1)

225

6.5

325

8.5

410

6.5

825

1650

21.5

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