LMH0030_0608 Datasheet, PDF (28/29 Pages) National Semiconductor (TI) – SMPTE 292M/259M Digital Video Serializer with Video and Ancillary Data FIFOs and Integrated Cable Driver

Application Information
Complete details for the SD130ASM evaluation PCB are
available on National’s WEB site. This circuit demonstrates
the capabilities of the LMH0030 and allows its evaluation in
a native configuration. An assembled demonstration board
kit, part number SD130EVK, complete with operating in-
structions, drawing package and list of materials is available.
Contact the Interface Products Group or the Serial Digital
Video and Interface Applications Group for ordering informa-
tion. Complete circuit board layouts, schematics and other
information for the SD130EVK are also available on Nation-
al’s WEB site in the application information for this device.
For latest product details and availability information, please
see: www.national.com/appinfo/interface.
PCB LAYOUT AND POWER SYSTEM BYPASS
RECOMMENDATIONS
Circuit board layout and stack-up for the LMH0030 should be
designed to provide noise-free power to the device. Good
layout practice also will separate high frequency or high level
inputs and outputs to minimize unwanted stray noise pickup,
feedback and interference. Power system performance may
be greatly improved by using thin dielectrics (4 to 10 mils) for
power/ground sandwiches. This increases the intrinsic ca-
pacitance of the PCB power system which improves power
supply filtering, especially at high frequencies, and makes
the value and placement of external bypass capacitors less
critical. External bypass capacitors should include both RF
ceramic and tantalum electrolytic types. RF capacitors may
use values in the range 0.01 µF to 0.1 µF. Tantalum capaci-
tors may be in the range 2.2 µF to 10 µF. Voltage rating for
tantalum capacitors should be at least 5X the power supply
voltage being used. It is recommended practice to use two
vias at each power pin of the LMH0030 as well as all RF
bypass capacitor terminals. Dual vias reduce the intercon-
nect inductance by up to half, thereby reducing interconnect
inductance and extending the effective frequency range of
the bypass components.
The outer layers of the PCB may be flooded with additional
V_SS (ground) plane. These planes will improve shielding and
isolation as well as increase the intrinsic capacitance of the
power supply plane system. Naturally, to be effective, these
planes must be tied to the V_SS power supply plane at fre-
quent intervals with vias. Frequent via placement also im-
proves signal integrity on signal transmission lines by pro-
viding short paths for image currents which reduces signal
distortion. The planes should be pulled back from all trans-
mission lines and component mounting pads a distance
equal to the width of the widest transmission line or the
thickness of the dielectric separating the transmission line
from the internal power or ground plane(s) whichever is
greater. Doing so minimizes effects on transmission line
impedances and reduces unwanted parasitic capacitances
at component mounting pads.
The LMH0030 uses two power supply voltages, 2.5 and 3.3
volts. These supplies connect to the device through seven
sets of independent power input pins. The function and
system supplied through these is given in the Pin Description
Table. The power supply voltages normally share a common
0 volt or ground return system. Either a split plane or sepa-
rate power planes can be used to supply the positive volt-
ages to the device.
In especially noisy power supply environments, such as is
often the case when using switching power supplies, sepa-
rate filtering may be used at the LMH0030’s PLL analog, PLL
digital and serial output driver power pins. The LMH0030
was designed for this situation. The digital section, PLL and
output driver power supply feeds are independent. See the
Pin Description Table and the Connection Diagram for de-
tails. Supply filtering may take the form of L-section or pi-
section, L-C filters in series with these V_DD inputs. Such
filters are available in a single package from several manu-
facturers. Despite being independent feeds, all device power
supplies should be applied simultaneously as from a com-
mon source.
PROCESSING NON-SUPPORTED AND pSf RASTER
FORMATS
The number and type of HD raster formats has proliferated
greatly since the LMH0030 was designed. Though not spe-
cifically capable of fully or automatically processing these
new formats, the LMH0030 may still be capable of serializing
them. The user is encouraged to experiment with processing
of these formats keeping in mind that the LMH0030 has not
been tested to handle raster formats other than those de-
tailed in Table 4. Therefore, the results from attempts to
process non-supported formats is not guaranteed. The fol-
lowing guidelines concerning device setup are provided to
aid the user in configuring the LMH0030 to attempt limited
processing of these other raster formats. In general, the
device is configured to defeat its format and TRS detection
function and to limit operation to a generic HD format type.
(The user should consult Table 4 for guidance on the format
groups similar to the non-supported one to be processed).
Since these newer formats are in the HD realm, the
LMH0030 should be configured to operate in HD-ONLY
mode by setting bit-5 of the FORMAT 0 register (address
0Bh). Also, the device should be further configured by load-
ing the FORMAT SET[4:0] bits of this register with a non-
specific HD sub-format code. The complete data word for
this HD sub-format code with HD-ONLY bit set is 33Fh (all 10
bits of AD[9:0]). Since this format differs from those in the
table, the EAV/SAV indicators are disabled. Without these
indicators, line numbering and CRC insertion are disabled
and ancillary data insertion will not function. Pre-processing
of the parallel data ahead of the LMH0030 will be required to
insert CRC data and line numbering.
Among the specialized formats are so-called progressive-
segmented frame formats (pSf). Refer to SMPTE 274M-
2003, Annex A. These formats are composed of the video
lines of progressive scan rasters rearranged in the manner
of an interlaced raster. The even numbered lines are ar-
ranged to form Field 1 and the odd numbered lines form
Field 2. In other respects, the format is identical to the
normal interlaced format. The LMH0030 can serialize these
pSf formats provided that the lines of the original progressive
raster are first rearranged externally to the LMH0030 before
being presented to it for processing.
www.national.com
28