LM2485

220V Triple Bias Clamp with G1 Blank Amplifier

General Description

The LM2485 is a triple channel clamp amplifier used to DC

restore the AC coupled outputs of a DTV CRT driver and for

cut-off adjustment. The LM2485 also has an integrated

blanking amplifier that can be used to drive the G1 grid of a

CRT negative for vertical retrace blanking. The blanking

output has a selectable pulse amplitude of either 20V

40V

be generated from a vertical flyback pulse or by a microcon-

troller.

The LM2485 can operate with a V

andaV

selectable via the Pin 12 option, ensures the LM2485 is

compatible with any National Semiconductor DTV CRT

driver sharing the same operating voltages in the applica-

tion.

The IC is packaged in an industry standard 24-lead molded

plastic dual-in-line package to meet high voltage spacing

requirements.

Features

n

V

n

V

n

Wide bias output voltage range of over 100V

n

Inverted output pulse suitable for G1 blanking,

selectable to 20V

Applications

n

AC coupled CRT applications using DTV formats up to

1080i

n

Well-matched to the NSC LM12XX Family of

Preamplifiers and LM242X/3X/5X Family of DTV CRT

Drivers

Pinout and Internal Block Diagram

20103433

FIGURE 1. Top View

Order Number LM2485NA

See NS Package Number N24C

December 2004

© 2004 National Semiconductor Corporation

DS201034

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