GB4571 Video Buffer with
Precision Strobed DC Restore
DATA SHEET
FEATURES
•
accurate clamping to within
±
1 mV
•
less than 1 mV clamping distortion
•
variable clamping range (V
EE
+ 3.0 V to V
CC
- 4.5 V)
•
ultra low differential gain and differential phase
•
fast recovery from sudden changes in DC offsets
•
less than
±
0.15
°
phase delay variation at 3.58 MHz
•
±
0.1 dB flatness to 80 MHz
•
±
4.5 V to
±
13.2 V supply voltage range
DESCRIPTION
The GB4571 is a high performance video buffer with DC
restore used primarily for accurate back porch clamping. Key
features include operation from
±
4.5 V to
±
13.2 V supply
voltages, fast recovery from sudden changes in DC offset,
±
0.1 dB flatness to 80 MHz and availability of industry standard
DIP and SOIC packages.
In the typical back porch clamping application, a negative
going back porch pulse from an external sync separator (such
as the GS4881 or GS4882) is applied to the GB4571's STROBE
input. While STROBE is low, the GB4571 determines the
correct DC level shift that should be applied to the input signal
by integrating over the entire back porch period. This reduces
sensitivity to noise and improves the accuracy of the DC
restoration compared to systems using sample and hold
techniques. Typical clamping accuracy of
±
1 mV is achieved
by the GB4571.
APPLICATIONS
PIN CONNECTIONS
GB4571
C
HOLD
V
IN
V
CLAMP
STROBE
1
2
3
4
8
7
6
5
V
CC
V
OUT
V
EE
GND
•
•
•
•
Clamping of NTSC, PAL, SECAM & RGB Video Signals
Multimedia Graphics Overlay
Production Switchers
Linear Keyers
SIMPLIFIED CIRCUIT DIAGRAM
AVAILABLE PACKAGING
VCC
8
8 pin PDIP
8 pin SOIC
V
IN
COUPLING
CAP
2
7
V
OUT
ORDERING INFORMATION
6
V
EE
Part Number
Package
Temperature Range
GB4571-CDA
GB4571-CKA
GB4571-CTA
8 pin PDIP
8 pin SOIC
8 pin SOIC Tape
0° to 70°C
0° to 70°C
NON-LNEAR
V TO
I
CONVERTER
HIGH Z
BUFFER
-
+
3
V
CLAMP
4
STROBE
0° to 70°C
5
GND
1
C
HOLD
Document No. 521 - 17 - 01
GENNUM CORPORATION P.O. Box 489, Stn A, Burlington, Ontario, Canada L7R 3Y3 tel. (905) 632-2996 fax: (905) 632-2055
Japan Branch: A-302, Miyamae Village, 2-10-42, Miyamae, Suginami-ku, Tokyo 168, Japan
tel. (03) 3247-8838
fax. (03) 3247-8839
GENNUM [ GENNUM CORPORATION ]
