TH72032KDC Melexis Inc, TH72032KDC Datasheet - Page 4

• Manufacturer Part Number: TH72032KDC
• Description: TRANSMITTER ASK SOIC8
• Manufacturer: Melexis Inc

Specifications of TH72032KDC

• Frequency: 868MHz, 915MHz
• Modulation Or Protocol: ASK
• Data Rate - Maximum: 40 kbps
• Power - Output: 9dBm
• Current - Transmitting: 13.4mA
• Data Interface: PCB, Surface Mount
• Antenna Connector: PCB, Surface Mount
• Voltage - Supply: 1.95 V ~ 5.5 V
• Operating Temperature: -40°C ~ 125°C
• Package / Case: 8-SOIC (0.154", 3.90mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Features: -
• Applications: -
• Memory Size: -
• Other names: Q4689527

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
18pF. 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.
2.2 ASK Modulation
The PLL transmitter can be ASK-modulated by
applying a data stream directly at the pin
ASKDTA. This turns the internal current
sources of the power amplifier on and off and
therefore leads to an ASK signal at the output.
2.3 Crystal Pulling
A crystal is tuned by the manufacturer to the
required oscillation frequency f
capacitance CL and within the specified calibra-
tion tolerance. The only way to pull the oscilla-
tion frequency is to vary the effective load ca-
pacitance CL
Figure 2 shows the oscillation frequency of a
crystal as a function of the effective load ca-
pacitance. This figure also illustrates the rela-
tionship between the external pulling capacitor
and the center frequency.
It can be seen that the pulling sensitivity in-
creases with the reduction of CL. For high-
accuracy ASK applications, a higher load ca-
pacitance should be chosen in order to reduce
the frequency drift caused by the tolerances of
the chip and the external pulling capacitor.
3901072032
Rev. 009
eff
seen by the crystal.
0
at a given load
Page 4 of 20
Fig. 2:
f
c
f
ASKDTA
0
1
Crystal pulling characteristic
Power amplifier is turned on (according
CL=
to the selected output power step)
CX1 CRO
CX1+CR O
Power amplifier is turned off
Description
ASK Transmitter
C1
L1
XTAL
R1
TH72032
868/915MHz
C0
Data Sheet
March/08
CL
CL
eff
eff