National Semiconductor LMH1251 Technical data
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LMH1251
YP
BPR
General Description
The LMH™1251 is a wideband 2:1 analog video switch with
an integrated YP
one set of YP
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 Standard Definition Television (SDTV) and High Definition Television (HDTV) inputs. It provides bi-level sync, and tri-level
sync separation.
The color space conversion from YP
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 vectorscope. It is equipped with a smart video detection circuit
which automatically senses SDTV and HDTV video formats
and applies the appropriate color space conversion.
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.
to RGB Decoder and 2:1 Video Switch
to RGB decoder. The device accepts
BPR
inputs and one set of RGB/HSYNC/
BPR
to RGB in the
BPR
August 2005
Features
n YPBPRto RGB decoding
n YP
n RGB path: 400 MHz, −3 dB, 700 mV
n Supports PC video display resolutions up to UXGA
n Supports 480i, 480p, 576i, 576p, 720p, 1080i, and
n Smart video format detection for SD and HD
n Power save mode
path: 70 MHz, −3 dB, 700 mVPPbandwidth
BPR
(1600 x 1200
1080p
@
75 Hz)
bandwidth
PP
Applications
n TFT LCD monitor
n CRT monitor
n Set-top box
n Display projector
LMH1251 YP
B
P
R
to RGB Decoder and 2:1 Video Switch
Connection Diagram
24-Pin TSSOP
20151927
Top View
LMH™is a trademark of National Semiconductor Corporation.
© 2005 National Semiconductor Corporation DS201519 www.national.com
Truth Table
TABLE 1. Input Select
LMH1251
TABLE 2.
Pin 23 Pin 22 SYNC Format Detection Decoding Scheme
0 0 Bi-Level Manual 480p
0 1 Tri-Level Manual 720p/180i
1 *Outputs 0 Bi-Level Auto 480p
1 *Outputs 1 Tri-Level Auto 720p/1080i
Pin 24 OUT
0 RGBhv input Ch
1YP
BPR
input Ch
Note: * When Pin 23 is set high, the LMH1251 is inAuto Mode, in which it can
detect the incoming video format (SD or HD) and apply the appropriate
color decoding and sync processing. WithAuto 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
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 theAuto Mode with Pin 22 left floating is typically
recommended.
TABLE 3. Power Save
Pin 21 Low Power Mode
0 Disable
1 Enabled
Ordering Information
Package Part Number Package Marking Transport Media NSC Drawing
24-Pin TSSOP
LMH1251MT
LMH1251MTX 2.5k Units Tape and Reel
LMH1251MT
61 Units/Rail
MTC24
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LMH1251
Absolute Maximum Ratings (Notes 1, 3)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
ESD Tolerance
Susceptibility(Note 4) 4.0 kV
Thermal Resistance to Case
) 25˚C/W
(θ
JC
Junction Temperature (T
) +150˚C
J
Storage Temperature Range −65˚C to +150˚C
Lead Temperature (soldering 10
sec.) 265˚C
Machine Model (Note 11) 400V
Supply Voltage V
, Pins 7
CC
Operating Ratings (Note 2)
and 17 5.5V
Voltage at any Input Pin (V
Video Inputs (pk-pk) 0.0V ≤ V
)VCC−0.5 ≥ VIN≥ 0V
IN
≤ 1.2V
IN
Thermal Resistance to Ambient
(θJA) 110˚C/W
Operating Temperature Range 0˚C to +70˚C
Supply Voltage (V
RGB Video Inputs (pk-pk) 0.0V ≤ V
Y Video Inputs (incl. Sync) -0.3V ≤ V
P
Video Inputs -0.35V ≤ VIN≤ 0.35V
BPR
) 4.75V ≤ VCC≤ 5.25V
CC
IN
IN
Video Signal Electrical Characteristics
Unless otherwise noted: TA= 25˚C, VCC= +5.0V, RGB VideoIN= 0.70, Y VideoIN= 0.7 VPP,PBPRVideoIN=±350 VmV,
= 8 pF, Video Outputs = 0.7 VPP. See (Note 7) for Min and Max parameters and (Note 6) for typicals.
C
L
Symbol Parameter Conditions (Note 2) Min Typ Max Units
I
S, RGB
I
,YPBP
R
S
I
S-PS
I
OUT
V
O BLK
Gain
RGB
Ch-Ch
Match
RGB
LE
RGB
Video Time Domain Response
RGB t
r
RGB OS
RGB t
RGB OS
R
f
F
SD YPBPRt
RGB OSF RGB Input:
SD YP
BPRtr
SD YP
BPROSR
SD YP
BPRtf
SD YPBPROSFSD YPBPR:
Supply Current No Output Loading, 80 kHz 28 34 41 mA
Supply Current No Output Loading, 480p
60 70 80 mA
see (Note 8)
Supply Current, Power Save
Mode
Power Save Mode, No Output
Loading, 80 kHz, see (Note 8)
4 8 12 mA
Output Current 3 mA
Typical DC Active Video Black
No AC Input Signal 1.8 2.1 2.4 VDC
Level Output Voltage
RGB Video Unity Gain RGB VideoIN= 0.7 V
RGB Ch to Ch Matching RGB VideoIN= 0.7 V
RGB Input: Linearity Error Staircase Input Signal
PP
PP
0.07 dB
0.02 dB
0%
see (Note 9)
RGB Input:
Video Rise Time
RGB Input:
Rising Edge Overshoot
RGB Input:
Video Fall Time
RGB Input:
Rising Edge Overshoot
SD YPBPRInput:
r
Video Rise Time
10% to 90%, AC Input Signal
(Note 5)
AC Input Signal
(Note 5)
90% to 10%, AC Input Signal
(Note 5)
AC Input Signal
(Note 5)
10% to 90%, AC Input Signal
(Note 5)
1.55 ns
3%
1.55 ns
3%
1.54 ns
(Note 5), AC Input Signal 3 %
Falling Edge Overshoot
SD YPBPRInput:
Video Rise Time
SD YPBPRInput:
Rising Edge Overshoot
SD YPBPR:
Video Fall Time
Falling Edge Overshoot
10% to 90%, AC Input Signal
(Note 5)
AC Input Signal
(Note 5)
90% to 10%, AC Input Signal
(Note 5)
AC Input Signal
(Note 5)
15.4 ns
3%
15.4 ns
3%
≤ 0.7V
≤ 0.7V
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