MLX72013 Datasheet, PDF (4/21 Pages) Melexis Microelectronic Systems – FSK/ASK Transmitter

MLX72013
433MHz
FSK/ASK Transmitter
6. Theory of Operation
6.1 General
As depicted in Fig.1, the MLX72013 transmitter consists of a fully integrated voltage-controlled oscillator
(VCO), a divide-by-16 divider (div16), a phase-frequency detector (PFD) and a charge pump (CP). An
internal loop filter determines the dynamic behavior of the PLL and suppresses reference spurious signals. A
Colpitts crystal oscillator (XOSC) is used as the reference oscillator of a phase-locked loop (PLL)
synthesizer. The VCO’s output signal feeds the power amplifier (PA). The RF signal power P_out can be
adjusted in four steps from P_out = –14 dBm to +11 dBm, either by changing the value of resistor RPS or by
varying the voltage V_PS at pin PSEL. The open-collector output (OUT) can be used either to directly drive a
loop antenna or to be matched to a 50Ohm load. Bandgap biasing ensures stable operation of the IC at a
power supply range of 1.95 V to 5.5 V.
6.2 Block Diagram
4
ENTX
m ode
control
VCC
6
P LL
16
ROI ³
XTAL
XOSC
FSKSW ²
CX2
CX1
1
FSKDTA
XBUF
8
VEE
PFD
CP
VC O
RPS
PSEL
5
PA
lo w
volt age
dete ctor
7 OUT ^{ante nna}
matc hi ng
network
Fig. 1: Block diagram with external components
3901072013
Rev. 007
Page 4 of 21
Data Sheet
Oct/14