U2860B-MFPY Atmel, U2860B-MFPY Datasheet - Page 3

• Manufacturer Part Number: U2860B-MFPY
• Description: IC DEMOD DUAL FM FOR TV 14SOIC
• Manufacturer: Atmel
• Type: Demodulatorr

Specifications of U2860B-MFPY

• Applications: Multimedia
• Mounting Type: Surface Mount
• Package / Case: 14-SOIC (3.9mm Width), 14-SOL
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

3. Circuit Description
4. Limiter Amplifiers
5. PLL FM Demodulators
6. Audio Amplifiers
7. Squelch Function
8. Mute Switch
9. Internal Voltage Stabilizer
4794E–TVVCR–12/05
The U2860B-M includes two identical sound IF channels. Each consists of a limiter amplifier,
PLL FM demodulator and AF amplifier. Additionally, this circuit contains a squelch function, mute
switch and internal voltage regulation.
The intercarrier signals are fed through external ceramic bandpass filters to a 7-stage limiter
amplifier. This guarantees high input sensitivity and excellent AM suppression.
The alignment-free Phase Locked Loop (PLL) demodulator covers a wide frequency range of
4.5 MHz up to 6.5 MHz with low-noise performance. The linear voltage to frequency characteris-
tic results in low harmonic distortion. The free-running frequency of the internal VCO circuit is
about 5.5 MHz. For this frequency, the input sensitivity and VCO locking is optimal. An additional
external resistor at pin 10 allows a frequency shift of ±1 MHz via an internal offset current. With
this option, it is possible to shift the optimum conditions to the upper frequency (6.5 MHz) or to
the lower frequency (4.5 MHz). The offset current acts simultaneously on both VCO circuits. If
no resistor is connected, the offset current is disabled.
The demodulated signals are amplified to 500 mVrms with low output impedance at the audio
outputs (pin 6 and pin 7). AC decoupling at pin 8 and pin 9 of the audio amplifiers leads to high
common mode rejection.
For channel 2 the audio output amplifier and VCO2 is muted automatically (squelch) when the
second sound carrier is not present. This avoids a wrong identification for stereo and dual sound
in the stereo decoder. Therefore, with mono sound, there is no output signal at pin 6. The auto-
matic squelch function can be disabled by switching pin 4 to ground.
Simultaneous muting of both circuits is possible by switching pin 3 to ground.
The internal bandgap reference ensures constant performance independent of supply voltage
and temperature.
U2860B-M
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