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PDF GS4882 Data sheet ( Hoja de datos )
| Número de pieza | GS4882 | |
| Descripción | Video Sync Separators | |
| Fabricantes | Gennum | |
| Logotipo |  |
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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
1 page  
2. Circuit Description
The Block Diagrams for the GS4882 and GS4982 are shown in Figure 2-6 and Figure 2-7,
with timing diagrams for the devices shown in Figure 2-8.
When presented with a composite video input signal, the GS4882 outputs composite
sync, vertical sync, back porch and odd/even field information. The GS4982 substitutes
the composite sync output with a horizontal sync output, for those applications
requiring horizontal sync extraction.
An external resistor, RSET, connected to Pin 6 is used to set all timing currents in the
device. For standard NTSC applications, RSET should be set to 227kΩ. The value of RSET
for a standard NTSC application is different for the GS4882/GS4982 line of sync
separators (RSET = 227kΩ) than it is for the GS1881/GS4881/GS4981 line of sync
separators (RSET = 680kΩ). This change was made to improve jitter performance of the
device.
2.1 Composite Video Input (Pin 2)
The GS4882 and GS4982 will operate with input signal amplitudes ranging from 0.5V to
4.0Vp-p. Composite video is AC coupled into the device via an external coupling
capacitor connected to Pin 2.
Immediately upon entering the GS4882/GS4982, the video signal is passed to the
device’s dual mode input clamp in order to clamp the sync tip of the input video
waveform to 1.55V. The GS4882/GS4982’s dual mode input clamp, with both Hard
Clamp and Soft Clamp capabilities, has been specifically designed for use in high
performance sync separation. The dual mode input clamp aids in maintaining the
accuracy of the internally derived 50% sync slicing level to within ±5% by utilizing the
Soft Clamp during steady state operation. The device improves system start-up and
impulse noise recovery time by utilizing the device’s Hard Clamp and Nosync Recovery
Current during initial start-up and when steady state operation has been disturbed by
impulse noise.
During the clamping operation, the input video signal is passed through the device's
internal color burst filter. The internal filter attenuates the color burst by typically
>15dB. Figure 2-1 shows the typical frequency response of the internal color burst filter.
GS4882, GS4982 Video Sync Separators with 50% Sync
Slicing
Data Sheet
8505 - 2
November 2009
5 of 13
Proprietary & Confidential
5 Page 
COMPOSITE
VIDEO INPUT
COMPOSITE SYNC OUTPUT
GS4882
BACK PORCH OUTPUT
GS4882, GS4982
HORIZONTAL OUTPUT
GS4982
VERTICAL SYNC OUTPUT
GS4882, GS4982
525
ODD/EVEN OUTPUT
GS4882, GS4982
12
34
5
6
HSYNC INTERNAL 600ns
2.5μs
78
COMPOSITE
VIDEO INPUT
BACK PORCH
OUTPUT
525ns
Figure 2-8: GS4882, GS4982 Video Sync Separator Timing Diagram
2.5μs
VIDEO
75Ω
VCC
0.1
VEE
0.1
10
VCLAMP
0.1
86
GB4571
2 STROBED 7
DC RESTORE
31
45
CHOLD
1.0nF
2
GS4882 8
SYNC
SEPARATOR
45
6
227k
0.1
VCC
0.1
BACK
PORCH
PULSE
ROUT
CLAMPED
VIDEO
CL OUTPUT
NOTE: All resistors in ohms, all capacitors in microfarads, unless otherwise stated.
Figure 2-9: Typical NTSC Application Diagram
GS4882, GS4982 Video Sync Separators with 50% Sync
Slicing
Data Sheet
8505 - 2
November 2009
11 of 13
Proprietary & Confidential
11 Page | ||
| Páginas | Total 13 Páginas | |
| PDF Descargar | [ Datasheet GS4882.PDF ] | |
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