EVB72006 Melexis Company, EVB72006 Datasheet - Page 3

• Manufacturer Part Number: EVB72006
• Description: Evaluation Board For Th72006
• Manufacturer: Melexis Company

1 Theory of Operation
1.1 General
As depicted in Fig.1, the TH72006 transmitter consists of a fully integrated voltage-controlled oscillator
(VCO), a divide-by-32 divider (div32), a phase-frequency detector (PFD) and a charge pump (CP). An inter-
nal 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) synthe-
sizer. The VCO’s output signal feeds the power amplifier (PA). The RF signal power P
four steps from P
voltage V
or to be matched to a 50 Ohm load. Bandgap biasing ensures stable operation of the IC at a power supply
range of 1.95 V to 5.5 V.
1.2 Block Diagram
2 Functional Description
2.1 Crystal Oscillator
A Colpitts crystal oscillator with integrated functional capacitors is used as the reference oscillator for the PLL
synthesizer. The equivalent input capacitance CRO offered by the crystal oscillator input pin ROI is about
18 pF. The crystal oscillator is provided with an amplitude control loop in order to have a very stable fre-
quency over the specified supply voltage and temperature range in combination with a short start-up time.
39012 72006 01
Rev. 004
CX1
XTAL
CX2
FSKSW
PS
CKOUT
ROI
at pin PSEL. The open-collector output (OUT) can be used either to directly drive a loop antenna
3
2
out
5
= –12 dBm to +11 dBm, either by changing the value of resistor RPS or by varying the
FSKDTA
XOSC
div 16
div 4
1
Fig. 1:
CKDIV
XBUF
7
Block diagram with external components
PLL
PFD
CP
32
Page 3 of 12
VCC
VCO
10
RPS
315MHz FSK/ASK Transmitter
PSEL
Evaluation Board Description
control
mode
PA
6
R1
9
VEE
ASKDTA
8
4
EVB72006
OUT
EN
out
can be adjusted in
matching
antenna
network
EVB Description
Dec/07