This noise blanker integrated circuit contains all of the necessary

circuitry for adding an extremely efficient (patented) noise-blanking

technique to any type of AM tuner or receiver with RF input frequen-

cies (or a first IF) to 30 MHz. The A3845ELW and A3845SLW

feature dual audio channels and are intended for AM-stereo or indepen-

dent sideband applications.

A high input impedance, high-gain, broadband RF amplifier

permits these devices to be directly connected to the RF stage of a

tuner. Internal AGC circuitry ensures that the noise detection threshold

remains constant with changes in input signal level. The RF gate

response time is sufficiently fast to blank the noise pulse at the output

of the mixer before the IF filter. Short blanking times effectively

suppress most of the interfering noise. Residual audio noise is re-

moved by an audio sample-and-hold gate. The RF blanking time,

audio gate delay time, and audio gate blanking time can all be indepen-

dently adjusted to suit the particular application.

These AM noise blankers are packaged in plastic SOICs and are

rated for operation over the a standard temperature range of -20

°C to

+85

°C (suffix ‘SLW’) or an extended temperature range to -40°C

(suffix ‘ELW’).

AM NOISE BLANKER

ABSOLUTE MAXIMUM RATINGS

12 V

Package Power Dissipation,

Suffix ‘ELW’ . . . . . . . .

-40

Suffix ‘SLW’ . . . . . . . .

-20

Storage Temperature Range,

FEATURES

I RF Blanking to 30 MHz

I Single-Channel or Stereo Audio Blanking

I Adjustable RF and Audio Blanking Time

I Adjustable Audio Blanking Delay

I Sample-and-Hold MOS Audio Gates

I Internal Voltage Regulation

I Minimum External Components

APPLICATIONS

I AM and AM-Stereo Automotive Radios

I CB Transmitter/Receivers

I Short-Wave Receivers

I Mobile Communications Equipment

3845

Always order by complete part number:

Part Number

Function

A3845ELW

Stereo Noise Blanker, Extended Temp. Range

A3845SLW

Stereo Noise Blanker, Standard Temp. Range

GROUND

13

14

15

16

17

19

12

18

20

11

1

2

3

8

9

4

5

6

7

10

RF AGC

SUPPLY

CC

V

AUDIO DELAY

RF BIAS

AUDIO BLANK

TIME (R)

AUDIO BLANK

TIME (C)

RF BLANK

TIME

NO

CONNECT

NO

CONNECT

NC

NC

Dwg. PS-003-1A

RF GATE

LOW

RF IN

RF BYPASS

NO

CONNECT

NC

RF GATE

HIGH

DET

NOISE

DIFFERENTIATOR