STDVE001A Datasheet, PDF (13/49 Pages) STMicroelectronics – Adaptive single 3.4 Gbps TMDS/HDMI signal equalizer

STDVE001A
3
Functional description
Functional description
The STDVE001A 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 STDVE001A result in a very
small propagation delay. Additionally, it supports the DDC, HPD and CEC signaling.
The I²C interface of the enabled input port is linked to the I²C interface of the output port,
and the hot plug detector (HPD) of the enabled input port is output to HPD_EXT.
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 V_CC 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 = 00 is
recommended on EQ pins for optimized operation.
Table 3. Adaptive equalizer gain with frequency
Freq (MHz)
Gain in dB
(EQ=00)
Gain in dB
(EQ=01)
Gain in dB
(EQ=10)
225
3
2
0
325
5
3
1
410
6.5
4.5
1.5
825
11
9
4
1650
16
14
8.5
Gain in dB
(EQ=11)
6.5
8.5
11
16
21.5
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