TDA7100 Datasheet, PDF (13/41 Pages) Infineon Technologies AG – 434 MHz ASK/FSK Transmitter in 10-pin Package

TDA7100
2.4
Functional Block Description
Functional Description
2.4.1 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 consisting of spiral inductors
and varactor diodes is on chip, too. Therefore no additional external components are
necessary. The nominal center frequency of the VCO is 868 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. The phase detector is a Type IV
PD with charge pump. The passive loop filter is realized on chip.
2.4.2 Crystal Oscillator
The crystal oscillator operates at 13.56 MHz.
The crystal frequency is divided by 16. The resulting 847.5 kHz are available at the clock
output CLKOUT (pin1) to drive the clock input of a micro controller.
To achieve FSK transmission, the oscillator frequency can be detuned by a fixed amount
by switching an external capacitor via FSKOUT (pin 4).
The condition of the switch is controlled by the signal at FSKDTA (pin 7).
Table 4
FSKDTA - FSK Switch
FSKDTA (pin7)
Low¹⁾
Open²⁾, High³⁾
FSK Switch
CLOSED
OPEN
1) Low:
2) Open:
3) High:
Voltage at pin < 0.5V
Pin open
Voltage at pin > 1.5V
2.4.3 Power Amplifier
The VCO frequency is divided by 2 and fed to the Power Amplifier.
The Power Amplifier can be switched on and off
by the signal at ASKDTA (pin 6).
Data Sheet
13
V 1.0, 2007-05-02