3845 Datasheet, PDF (1/8 Pages) Allegro MicroSystems – AM NOISE BLANKER

3845
AM NOISE BLANKER
RF IN 1
RF BYPASS 2
RF BIAS 3
RF AGC 4
AUDIO DELAY 5
AUDIO BLANK
TIME (R)
6
NO
CONNECT
7
NC
AUDIO BLANK ₈
TIME (C)
AUDIO OUT1 9
AUDIO IN1 10
DET
V_CC 20 SUPPLY
NC
19
NO
CONNECT
RF GATE
18 _LOW
17 ^{RF GATE}
HIGH
16 GROUND
15 ^{RF BLANK}
TIME
NC 14 ^NO
CONNECT
13 ^NOISE
DIFFERENTIATOR
12 AUDIO OUT2
11 AUDIO IN ₂
Dwg. PS-003-1A
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’).
ABSOLUTE MAXIMUM RATINGS
at T_A = +25°C
Supply Voltage, V_CC . . . . . . . . . . . . . . 12 V
Package Power Dissipation,
P_D . . . . . . . . . . . . . . . . . . . . . . . 1.78 W
Operating Temperature Range, T_A
Suffix ‘ELW’ . . . . . . . . -40°C to +85°C
Suffix ‘SLW’ . . . . . . . . -20°C to +85°C
Storage Temperature Range,
T_S . . . . . . . . . . . . . . . . -55°C to +125°C
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
Always order by complete part number:
Part Number Function
A3845ELW
A3845SLW
Stereo Noise Blanker, Extended Temp. Range
Stereo Noise Blanker, Standard Temp. Range