TDA5100A Datasheet, PDF (14/29 Pages) Infineon Technologies AG – ASK Transmitter 434 MHz

TDA 5100A
preliminary
Functional Description
3.4 Functional Blocks
3.4.1 PLL Synthesizer
The Phase Locked Loop synthesizer consists of a Voltage Controlled Oscillator
(VCO), an asynchronous divider chain, a phase detector, a charge pump and a
loop filter. It is fully implemented on chip. The tuning circuit of the VCO consist-
ing of spiral inductors and varactor diodes is on chip, too. Therefore no addi-
tional external components are necessary. The nominal center frequency of the
VCO is 869 MHz. The oscillator signal is fed both, to the synthesizer divider
chain and to the power amplifier. The overall division ratio of the asynchronous
divider chain is 64, a 13.56 MHz crystal should be used. The phase detector is
a Type IV PD with charge pump. The passive loop filter is realized on chip.
3.4.2 Crystal Oscillator
The crystal oscillator operates at 13.56 MHz.
The output frequency at CLKOUT (pin 6) is 3.39 MHz, this is the crystal fre-
quency divided by 4.
3.4.3 Power Amplifier
The VCO frequency 866-870 MHz is divided by 2 and fed to the power amplifier.
The Power Amplifier can be switched on and off
by the signal at DATA (pin 5).
Table 3-3
DATA (pin 5)
Low¹⁾
Open²⁾, High³⁾
1) Low: Voltage at pin < 0.5 V
2) Open: Pin open
3) High: Voltage at pin > 1.5 V
Power Amplifier
OFF
ON
The Power Amplifier has an Open Collector output at PAOUT (pin 9) and
requires an external pull-up coil to provide bias. The coil is part of the tuning and
matching LC circuitry to get best performance with the external loop antenna.
To achieve the best power amplifier efficiency, the high frequency voltage swing
at PAOUT (pin 9) should be twice the supply voltage.
The power amplifier has its own ground pin PAGND (pin 8) in order to reduce
the amount of coupling to the other circuits.
Wireless Components
3-7
Specification, March 2001