STDVE001ABTR STMICROELECTRONICS [STMicroelectronics], STDVE001ABTR Datasheet - Page 14

• Manufacturer Part Number: STDVE001ABTR
• Description: Adaptive single 3.4 Gbps TMDS/HDMI signal equalizer
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

Functional description
14/49
Figure 7.
The equalizer of STDVE001A is fully adaptive and automatic in function. The default setting
of EQ = 00 is recommended for optimal operation. The equalizer performance is optimized
for all frequencies over the cable lengths from 1m to 25 m at EQ = 00. If cable lengths
greater than 25 m are desired in application, then EQ = 11 setting is recommended. The
other two EQ settings of 01 and 10 are provided simply for fine-tuning purposes and can be
used for very short external cables or PCB traces only if deemed necessary.
Input termination
The STDVE001A integrates precise 50
its differential input channels. External terminations are not required. This gives better
performance and also minimizes the PCB board space. These on-chip termination resistors
should match the differential characteristic impedance of the transmission line. Since the
output driver consists of current steering devices, an output voltage is not generated without
a termination resistor. Output voltage levels are dependent on the value of the total
termination resistance. The STDVE001A produces TMDS output levels for point-to-point
links that are doubly terminated (100
the STDVE001A produces an output voltage of 3.3 – 0.5 V = 2.8 V when driving a
termination line terminated at each end. The input terminations are selectable thus saving
power for the unselected ports.
Output buffers
Each differential output of the STDVE001A drives external 50
conforms to the TMDS voltage standard. The output drivers consist of 10 mA differential
current-steering devices.
The driver outputs are short-circuit current limited and are high-impedance to ground when
OE_N = H or the device is not powered. The current steering architecture requires a
resistive load to terminate the signal to complete the transmission loop from V
through the termination resistor. Because the device switches the direction of the current
flow and not voltage levels, the output voltage swing is determined by V
drop across the termination resistor. The output current drivers are controlled by the OE_N
pin and are turned off when OE_N is a high. A stable 10 mA current is derived by accurate
internal current mirrors of a stable reference current which is generated by band-gap voltage
across the REXT. The differential output driver provides a typical 10 mA current sink
capability, which provides a typical 500 mV voltage drop across a 50
STDVE001A gain vs. frequency
25
20
15
10
5
0
225
325
Gain v/s Freq (STDVE001A)
Ω
Freq (MHz)
Ω
at each end). With the typical 10 mA output current,
410
± 5% termination resistors, pulled up to V
825
1650
Ω
load (pull-up resistor) and
Gain (EQ=00)
Gain (EQ=01)
Gain (EQ=10)
Gain (EQ=11)
Ω
CC
termination resistor.
minus the voltage
CC
STDVE001A
to GND
CC
, on all