TDA 4360X

Semiconductor Group

5

04.96

2

Circuit Description

The integrated circuit includes an 2-pin oscillator (1. LO) with sym. input, buffered output

and a double balanced mixer with sym. input. These stages convert the AM input signal

to a 1. IF which is much higher (~ 10 MHz) than the input frequencies. The 1. LO

operates as a LC varactor oscillator in the same 100 MHz range like the FM tuner

oscillator (e.g. TUA 4310X). So the same peripheral elements can be used.

Depending on the signal strength the prestage AGC controls MOSFET prestage

amplifiers.

The 1. IF passes an external selectivity and is then converted in a sym. double balanced

mixer to the 2. IF.

The 2. LO operates as a quartz controlled oscillator or as an amplifier for an external

signal.

The 2. IF signal passes an automatic gain controlled (AGC) IF amplifier and is then

demodulated to the AF in a quasi-synchronous demodulator. The AGC time constant

can be switched with a ratio of 20.

For fine tuning the decoupled 2. IF frequency is available.

The TDA 4360X is prepared to work with a PLL in the 100 MHz range. When applied

with a standard AM-PLL the oscillator frequency divided by 8 or 10 has to be used. In

this case a higher phase noise is to be expected.