Datasheet

User's Guide
SNOA526A–June 2008–Revised April 2013
AN-1836 LMH1251 Evaluation Board v2.0
1 Introduction
The LMH1251 evaluation board is designed for bench evaluation and characterization of the LMH1251
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.
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).
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 MΩ probe.
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1
SNOA526A–June 2008–Revised April 2013 AN-1836 LMH1251 Evaluation Board v2.0
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