U2861B Datasheet, PDF (2/11 Pages) TEMIC Semiconductors – Mono FM Sound Demodulator for TV Systems

U2861B
Circuit Description
Sound IF Limiter Amplifier
The intercarrier signal coming from the sound filter is fed
to a 7-stage limiter amplifier. This guarantees high input
sensitivity and excellent AM suppression.
PLL – FM Demodulator
The alignment-free “Phase-Locked-Loop” (PLL) FM
demodulator covers a wide frequency range of 4.5 MHz
up to 6.5 MHz with excellent noise performance. Due to
the fact that the voltage-to-frequency characteristic is
linear, a low harmonic distortion can be achieved. The
free-running frequency of the internal VCO circuit is
about 5.5 MHz.
The demodulated FM signal is led via de-emphasis and
W ^{buffered to Pin 12. The de-emphasis low pass filter con-}
sists of an internal 5-k series resistor and an external
capacitor at Pin 14. The FM muting is possible by switch-
ing Pin 5 to ground.
Audio Switch 1
The first audio switch (Pin 13) has inputs for the demodu-
lated FM signal and the external AF1 signal from Pin 1.
For multistandard purposes, it is possible to handle inter-
nal FM and external AM audio signals. The output of
switch1 is also permanently available at Pin 12 (e. g. for
SCART interface).
Audio Switch 2 and Volume Control
The second audio switch (Pin 11) has inputs for the audio
signal from switch 1 and the external AF2 signal at Pin 10.
The switched AF signal is fed to volume control. The out-
put voltage can be controlled by a DC voltage at Pin 9.
Internal Voltage Stabilizer
The internal bandgap reference ensures constant perfor-
mance independent of supply voltage and temperature.
Pin Description
Pin Symbol
Function
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ₁
v_i,AF1 Audio input 1 (e.g. AM signal)
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ₂
C_dec Decoupling capacitor
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ 3
v_i,SIF FM sound IF input
4
GND Ground
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ₅
V_mute FM mute switch
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ₆
C_ref
Internal reference voltage
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ₇
V_s
Supply voltage
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ₈
v_o,AF2 Switched audio output 2
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ₉
V_vol Volume control
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ 10
v_i,AF2 Audio input 2
(e.g. from SCART)
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ₁₁
Vsw₂ Audio switch 2
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ₁₂
v_o,AF1 Switched audio output 1
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ₁₃
Vsw₁ Audio switch 1
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ₁₄
C_dem De-emphasis and mute switch
v_i,AF1 1
14 C_dem
C_dec 2
13 _VSW1
v_i,SIF 3
12 v_o,AF1
GND 4 ^{U2861B 11} V_SW2
V_mute 5
10 v_i,AF2
C_ref 6
9 _Vvol
V_S 7
8 v_o,AF2
96 11833
Figure 2. Pinning
2 (11)
TELEFUNKEN Semiconductors
Preliminary Information
Rev. A1, 20-May-97