U2861B-MFPY71 Atmel, U2861B-MFPY71 Datasheet - Page 2

• Manufacturer Part Number: U2861B-MFPY71
• Description: RF Wireless Misc COM.VIDEO FM DEMODLTR (MONO)
• Manufacturer: Atmel

Specifications of U2861B-MFPY71

• Package / Case: SOIC
• Mounting Style: SMD/SMT

2. Circuit Description
2.1
2.2
2.3
2.4
2
PLL - FM Demodulator
Audio Switch 1
Audio Switch 2 and Volume Control
Internal Voltage Stabilizer
U2861B [Preliminary]
Sound IF Limiter Amplifier
The intercarrier signal coming from the sound filter is fed to a 7-stage limiter amplifier. This guar-
antees high input sensitivity and excellent AM suppression.
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 buffered to pin 12. The de-emphasis
low-pass filter consists of an internal 5-k series resistor and an external capacitor at pin 14.
The FM muting is possible by switching pin 5 to ground.
The first audio switch (pin 13) has inputs for the demodulated FM signal and the external AF1
signal from pin 1.
For multistandard purposes, it is possible to handle internal FM and external AM audio signals.
The output of switch1 is also permanently available at pin 12 (e.g., for SCART interface).
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 output voltage can be
controlled by a DC voltage at pin 9.
The internal band-gap reference ensures constant performance independent of supply voltage
and temperature.
4798B–TVVCR–07/05