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.

• Clamping of NTSC, PAL, SECAM & RGB Video Signals

• Multimedia Graphics Overlay

• Production Switchers

• Linear Keyers

Part Number

Package

Temperature Range

GB4571-CDA

8 pin PDIP

0

° to 70°C

GB4571-CKA

8 pin SOIC

0

° to 70°C

GB4571-CTA

8 pin SOIC Tape

0

° to 70°C

DATA SHEET

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

GB4571 Video Buffer with

Precision Strobed DC Restore

FEATURES

DESCRIPTION

AVAILABLE PACKAGING

8 pin PDIP

8 pin SOIC

PIN CONNECTIONS

1

2

3

4

8

7

6

5

V

CC

V

OUT

V

EE

GND

C

HOLD

V

IN

V

CLAMP

STROBE

GB4571

ORDERING INFORMATION

APPLICATIONS

• accurate clamping to within

• 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

•

•

Document No. 521 - 17 - 01

SIMPLIFIED CIRCUIT DIAGRAM

GND

VCC

COUPLING

CAP

STROBE

-

+

7

3

1

5

2

HIGH Z

BUFFER

NON-LNEAR

V TO

I

CONVERTER

4

6

8