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GS4882 Schematic ( PDF Datasheet ) - Gennum

Teilenummer GS4882
Beschreibung Video Sync Separators
Hersteller Gennum
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Gesamt 13 Seiten
GS4882 Datasheet, Funktion
GS4882, GS4982 Video Sync Separators with 50% Sync Slicing
Features
• precision 50% sync slicing
• internal color burst filter
• ±5ns temperature stability
• superior noise immunity
• robust signal detection/output muting circuitry
• high performance dual mode input clamp
• 0.5V to 4.0Vpp input signal with +5V supply
• composite, vertical, back porch, odd/even outputs
• horizontal sync output available with GS4982
• +4.5V to +13.2V supply voltage range
• Pb-free and Green
Description
The GS4882 and GS4982 are precision sync separators for
extracting timing information from NTSC, PAL, and SECAM
video signals. The GS4882 generates noise immune and
temperature stable composite sync, vertical sync, back
porch and odd/even field signals. The GS4982 provides a
horizontal sync output for those applications requiring
horizontal sync extraction.
The GS4882 and GS4982 feature an internal color burst
filter for minimization of spurious timing information and
the reduction of external component count. The precision
50% sync slicing feature embodied in the device provides
for superior sync extraction in the presence of noise and
varying sync pulse amplitudes. The high performance dual
mode input clamp aids in maintaining the accuracy of the
internally derived 50% sync slicing level to within ±5% as
well in reducing system start-up/recovery time. In
addition, a missing pulse detector enables the devices to
quickly respond to impulse noise by temporarily turning on
a Nosync Recovery Current connected to the dual mode
input clamp. The input stage will operate with input signal
amplitudes ranging from +0.5 to +4.0V peak to peak with a
+5V supply voltage.
The GS4882 and GS4982 have robust signal detection and
output muting circuitry. Should valid video be removed
from the device input, the absence of video will be
automatically detected and all outputs muted to a logic
high state after a defined probation period. Upon the return
of a valid video signal, device outputs are enabled after
receiving 8 lines of video. An internal frequency to voltage
converter also allows the device to differentiate between
valid and invalid input signals by analyzing the horizontal
scan rate of the input signal and comparing it against the
expected input signal scan rate.
The GS4882 and GS4982 are available in standard 8-pin
PDIP and SOIC packages, operate with a +4.5V to +13.2V
supply voltage range and typically consume less than 6mA
of current with a +5V supply voltage.
COMPOSITE
SYNC OUT
COMPOSITE
VIDEO IN
VERTICAL
SYNC OUT
GROUND
GS4882
18
27
36
45
Vcc
ODD/EVEN
RSET
BACK PORCH
GS4982
HORIZONTAL
COMPOSITE
VIDEO IN
VERTICAL
SYNC OUT
GROUND
1
2
3
4
8
7
6
5
Vcc
ODD/EVEN
RSET
BACK PORCH
Figure A: Pin Connections
GS4882, GS4982 Video Sync Separators with 50% Sync
Slicing
Data Sheet
8505 - 2
November 2009
www.gennum.com
1 of 13
Proprietary & Confidential






GS4882 Datasheet, Funktion
0
-5
-15
-25
-35
0.01
0.1 1
FREQUENCY (MHz)
10
Figure 2-1: Frequency Response of Internal Color Burst Filter
2.2 Composite Sync Output (Pin 1 GS4882)
The filtered video signal is then fed to a comparator which compares it to an internally
derived voltage corresponding to the 50% point of the sync pulse amplitude.
By slicing the composite video waveform at 50% of the sync pulse amplitude, variations
in output pulse timing due to variations in input signal amplitude are minimized.
Figure 2-2 demonstrates the stability of output pulse timing achieved with 50% sync
slicing.
With 50% Sync Slicing no Time Base Errors (TBEs) are introduced due to variations in
sync pulse amplitude. Output pulses are always produced at tO+tD , where tD represents
the delay through the device.
A Sync Pulse No.1
A/2 Sync Pulse No.2
50% Slice
50% Slice
to
Time
Figure 2-2: Stability of Output Pulse Timing with Variations in Sync Pulse
Amplitude
The 50% point of sync is determined by using two identical resistors to divide the voltage
between sync tip and back porch. The importance of precision sync tip clamping may be
GS4882, GS4982 Video Sync Separators with 50% Sync
Slicing
Data Sheet
8505 - 2
November 2009
6 of 13
Proprietary & Confidential

6 Page









GS4882 pdf, datenblatt
3. Ordering Information
Table 3-1: GS4882 Ordering Information
Part Number
GS4882-CDA
GS4882-CKA
GS4882-CTA
GS4882-CKAE3
Package
8-Pin PDIP
8-Pin SOIC
8-Pin SOIC Tape
8-Pin SOIC
Temperature
Range
0°C to 70°C
0°C to 70°C
0°C to 70°C
0°C to 70°C
Pb-Free and Green
No
No
No
Yes
Table 3-2: GS4982 Ordering Information
Part Number
GS4982-CDA
GS4982-CKA
GS4982-CTA
GS4982-CKAE3
Package
8-Pin PDIP
8-Pin SOIC
8-Pin SOIC Tape
8-Pin SOIC
Temperature
Range
0°C to 70°C
0°C to 70°C
0°C to 70°C
0°C to 70°C
Pb-Free and Green
No
No
No
Yes
GS4882, GS4982 Video Sync Separators with 50% Sync
Slicing
Data Sheet
8505 - 2
November 2009
12 of 13
Proprietary & Confidential

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