TDA5204 Просмотр технического описания (PDF) - Infineon Technologies

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TDA5204

ASK Single Conversion Receiver 390MHz

Infineon Technologies 

TDA 5204 E1

preliminary

Functional Description

ing case and interference scenario to be expected during operation. The opti-

mum choice of AGC time constant and the threshold voltage is described in

Section 4.1.

3.4.2 Mixer

The Double Balanced Mixer downconverts the input frequency (RF) 390MHz to

the intermediate frequency (IF) at 10.7MHz with a voltage gain of approximately

21dB. A low pass filter with a corner frequency of 20MHz is built on chip in order

to suppress RF signals to appear at the IF output ( IFO pin). The IF output is

internally consisting of an emitter follower that has a source impedance of

approximately 330Ω= to facilitate interfacing the pin directly to a standard

10.7MHz ceramic filter without additional matching circuitry.

3.4.3 PLL Synthesizer

The Phase Locked Loop synthesiser consists of a VCO, an asynchronous

divider chain, a phase detector with charge pump and a loop filter and is fully

implemented on-chip. The VCO is including spiral inductors and varactor

diodes. It’s nominal centre frequency is 800MHz. The FSEL pin (Pin 11) has to

be left open. No additional components are necessary. The oscillator signal is

fed both to the synthesiser divider chain and to the downconverting mixer. The

VCO signal is divided by two before it is fed to the mixer. The loop filter is also

realised fully on-chip.

3.4.4 Crystal Oscillator

The on-chip crystal oscillator circuitry allows for utilisation of quartzes both in

the 6 and 12MHz range as the overall division ratio of the PLL can be switched

between 64 and 128 via the CSEL (Pin 16 ) pin according to the following table.

Table 3-2 CSEL Pin Operating States

CSEL

Open

Shorted to ground

Crystal Frequency

6.xx MHz

12.xx MHz

The calculation of the value of the necessary quartz load capacitance is shown

in Section 4.3, the quartz frequency calculation is expained in Section 4.4.

Wireless Components

3-9

Specification, December 2000

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