LMH1251 Switch Datasheet

LMH1251 Datasheet, PDF, Equivalent


Part Number

LMH1251

Description

YPBPR to RGB Decoder and 2:1 Video Switch

Manufacture

National Semiconductor

Total Page 10 Pages
Datasheet
Download LMH1251 Datasheet


LMH1251
www.DataSheet4U.com
August 2005
LMH1251
YPBPR to RGB Decoder and 2:1 Video Switch
General Description
Features
The LMH1251 is a wideband 2:1 analog video switch with
an integrated YPBPR to RGB decoder. The device accepts
one set of YPBPR inputs and one set of RGB/HSYNC/
VSYNC inputs. Based on the input selected, the output will
be either a decoded TV or buffered PC video signal.
The LMH1251 has a SYNC separator and processor that is
capable of extracting sync timing information from both Stan-
dard Definition Television (SDTV) and High Definition Tele-
vision (HDTV) inputs. It provides bi-level sync, and tri-level
sync separation.
n YPBPR to RGB decoding
n YPBPR path: 70 MHz, −3 dB, 700 mVPP bandwidth
n RGB path: 400 MHz, −3 dB, 700 mVPP bandwidth
n Supports PC video display resolutions up to UXGA
(1600 x 1200 @ 75 Hz)
n Supports 480i, 480p, 576i, 576p, 720p, 1080i, and
1080p
n Smart video format detection for SD and HD
n Power save mode
The color space conversion from YPBPR to RGB in the
LMH1251 is realized with a very high precision fully analog
dematrixer that provides chrominance accuracy that is less
than 2.5% of amplitude & 1.5˚ of phase error on a vector-
scope. It is equipped with a smart video detection circuit
which automatically senses SDTV and HDTV video formats
and applies the appropriate color space conversion.
Applications
n TFT LCD monitor
n CRT monitor
n Set-top box
n Display projector
The LMH1251 is capable of handling SDTV, HDTV, XGA,
SXGA, and UXGA video formats, which makes it an ideal
solution for enhancing value in applications ranging from
LCD monitors, to set-top boxes, to projectors. The LMH1251
is available in a TSSOP-24 package.
Connection Diagram
24-Pin TSSOP
Top View
LMHis a trademark of National Semiconductor Corporation.
© 2005 National Semiconductor Corporation DS201519
20151927
www.national.com

LMH1251
Truth Table
TABLE 1. Input Select
Pin 24
0
1
TABLE 2.
Pin 23
0
0
1
1
Pin 22
0
1
*Outputs 0
*Outputs 1
SYNC
Bi-Level
Tri-Level
Bi-Level
Tri-Level
Note: * When Pin 23 is set high, the LMH1251 is in Auto Mode, in which it can
detect the incoming video format (SD or HD) and apply the appropriate
color decoding and sync processing. With Auto Mode, Pin 22 becomes
an output pin, and will either output a logic high or low to notify the user
of the format that is being detected by the LMH1251. If Pin 23 is set
low, the LMH1251 is in Manual Mode, in which the user must specify
TABLE 3. Power Save
Pin 21
0
1
OUT
RGBhv input Ch
YPBPR input Ch
Format Detection
Manual
Manual
Auto
Auto
Decoding Scheme
480p
720p/180i
480p
720p/1080i
the format with Pin 22. With Manual Mode, Pin 22 is an input pin. Since
Pin 22 is a bi-directional pin, care must be taken to not apply any
voltages to it when it is in the Auto Mode, in which it functions as an
output pin. The use of the Auto Mode with Pin 22 left floating is typically
recommended.
Low Power Mode
Disable
Enabled
Ordering Information
Package
24-Pin TSSOP
Part Number
LMH1251MT
LMH1251MTX
Package Marking
LMH1251MT
Transport Media
61 Units/Rail
2.5k Units Tape and Reel
NSC Drawing
MTC24
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Features www.DataSheet4U.com LMH1251 YPBPR to RG B Decoder and 2:1 Video Switch August 2005 LMH1251 YPBPR to RGB Decoder and 2:1 Video Switch General Description Th e LMH™1251 is a wideband 2:1 analog v ideo switch with an integrated YPBPR to RGB decoder. The device accepts one se t of YPBPR inputs and one set of RGB/HS YNC/ VSYNC inputs. Based on the input s elected, the output will be either a de coded TV or buffered PC video signal. T he LMH1251 has a SYNC separator and pro cessor that is capable of extracting sy nc timing information from both Standar d Definition Television (SDTV) and High Definition Television (HDTV) inputs. I t provides bi-level sync, and tri-level sync separation. The color space conve rsion from YPBPR to RGB in the LMH1251 is realized with a very high precision fully analog dematrixer that provides c hrominance accuracy that is less than 2 .5% of amplitude & 1.5˚ of phase error on a vectorscope. It is equipped with a smart video detection circuit which automatically senses SDTV an.
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