Texas Instruments YPbPr to RGBHV Converter and 2:1 Video Switch LMH1251EVAL/NOPB LMH1251EVAL/NOPB Scheda Tecnica
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LMH1251EVAL/NOPB
User's Guide
SNOA526A – June 2008 – Revised April 2013
AN-1836 LMH1251 Evaluation Board v2.0
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Introduction
The LMH1251 evaluation board is designed for bench evaluation and characterization of the LMH1251
device.
device.
•
A VGA 15-pin D-sub PC video connector and YP
B
P
R
RCA component Video connector are installed on
the board for video source inputs 1 and 2, respectively.
•
JP1, JP2, JP3, and JP4 are used to set the logic selection pins 21 through 24, by installing the jumpers
in the appropriate configuration.
in the appropriate configuration.
Since the LMH1251 is not intended to directly drive a video cable, a LMH6739 op amp with a gain of 2 is
included on the board so that the output of the LMH1251 can be displayed on a monitor for visual
inspection. Logic inverters are also included at the outputs of the H and V Sync outputs to provide output
drive for the signals over the VGA cable. Typically, the LMH1251 is designed into a system board with
extremely minimal trace length, AC coupled to the next stage, which can be either an ADC (TFT LCD
monitor), or a preamplifier (CRT monitor).
included on the board so that the output of the LMH1251 can be displayed on a monitor for visual
inspection. Logic inverters are also included at the outputs of the H and V Sync outputs to provide output
drive for the signals over the VGA cable. Typically, the LMH1251 is designed into a system board with
extremely minimal trace length, AC coupled to the next stage, which can be either an ADC (TFT LCD
monitor), or a preamplifier (CRT monitor).
The LMH1251 evaluation board has test point pads right at the RGB, H and V sync outputs of the
LMH1251 for oscilloscope probing (TP4, TP5, TP6, TP11, and TP12). Minimal length test leads can be
soldered on these pads for probing with a low capacitance (<1 pF) FET probe such as the Tektronix
P6245 for AC transient response measurements. DC level measurements can be taken with a passive
probe such as the Tektronix P5050, 10 M
LMH1251 for oscilloscope probing (TP4, TP5, TP6, TP11, and TP12). Minimal length test leads can be
soldered on these pads for probing with a low capacitance (<1 pF) FET probe such as the Tektronix
P6245 for AC transient response measurements. DC level measurements can be taken with a passive
probe such as the Tektronix P5050, 10 M
Ω
probe.
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SNOA526A – June 2008 – Revised April 2013
AN-1836 LMH1251 Evaluation Board v2.0
Copyright © 2008–2013, Texas Instruments Incorporated