LMH1983 Evaluation Kit Users Guide
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INTRODUCTION
The LMH1983 Evaluation Kit (EVK) allows for the evaluation of the LMH1983
3G/HD/SD Video Clock Generator with Audio Clock. The LMH1983 device is
configured and controlled using National Semiconductor’s Analog Launch Pad (ALP)
software graphical user interface (GUI).
The GUI with the LMH1983 profile runs on Windows PC and can be used to program the
device’s control registers through the I
2
C interface. The Serial Peripheral Adapter (SPA)
board included in the kit provides I
2
C read/write control via the USB port of the PC with
the GUI. For more information about the GUI software and device register descriptions
and programming, please refer to the GUI software manual and LMH1983 datasheet.
Overview of LMH1983
The LMH1983 clock generator generates four video specific clocks. The device has four
PLLs in it.
PLL1 uses an external 27 MHz VCXO, and always generates a 27MHz reference
clock. This clock may be locked to an input reference which can be any of a
number of different types of reference – from video specific references to single
frequency reference signals.
PLL2 is dedicated to generating a 148.5 MHz clock (27 MHz * 5.5) , and is
locked to PLL1.
PLL3 is dedicated to generating a clock at 148.35 MHz (27 MHz * 5500/1001)
PLL4, by default is locked to PLL1, and generates a 24.576MHz clock which can
be used as an audio clock. PLL4 has a lot of versatility built in to it and can be
used for a broad variety of applications.
