u4467b ATMEL Corporation, u4467b Datasheet - Page 2

• Manufacturer Part Number: u4467b
• Description: Sound Demodulator
• Manufacturer: ATMEL Corporation

Circuit Description
IF Amplifier and AGC
The symmetrical IF input signal from the external SAW
filter is fed to the Pins 1 and 2. In L-standard, a bandpass
filter with the center frequency at the L-sound carrier is
used.
The amplifier consists of three AC-coupled wideband IF
stages. Each differential amplifier stage is gain controlled
by the AGC (Automatic Gain Control) voltage, available
at Pin 3. The output signal of the IF amplifier is applied
to the AM demodulator.
The IF-AGC is derived from the average level of the AM
sound. It controls the three-stage wideband amplifier to
provide a constant SIF signal to the AM demodulator.
Pin Description
U4467B
2 (7)
V
C
C
V
V
o,AM
AGC
REF
NC
NC
NC
i,IF
i,IF
1
2
3
4
5
6
7
8
Figure 2. Pinning
U4467B
13829
Preliminary Information
16
15
14
13
12
11
10
9
NC
NC
GND
NC
NC
NC
V
V
S
sw,mute
AM Demodulator
The alignment-free AM demodulator is realized by a syn-
chronous detector. The modulated IF signal from the
wideband IF amplifier output is multiplied in phase with
the limited IF signal to remove the AM. Then, the result-
ing AF signal of the demodulator output is fed to the
output amplifier and to the AGC stage.
Mute Switch
The AM sound output (Pin 6) can be muted in pulling
mute switch (Pin 10) to ’low’.
Internal Voltage Stabilizer
The internal bandgap reference voltage (4.25 V at Pin 4)
ensures constant performance independent of supply
voltage and temperature.
Pin
10
11
12
13
14
15
16
1
2
3
4
5
6
7
8
9
V
Symbol
V
C
C
GND
sw,mute
V
V
NC
NC
NC
NC
NC
NC
NC
NC
o,AM
V
AGC
REF
i,IF
i,IF
S
IF input (symmetrical)
IF input (symmetrical)
Capacitor for AGC time constant
Capacitor for internal reference
voltage
Not connected
AF output (AM sound)
Not connected
Not connected
Not connected
Mute switch
Not connected
Not connected
Ground
Supply voltage (5 V)
Not connected
Not connected
Function
Rev. A1, 23-Apr-99