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TH72035
Transmitter - 868/915MHz, FSK/ASK (10L QFN 3x3 Dual)
 Download TH72035 Datasheet (PDF)
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TH72035 General Description
The TH72035 FSK/ASK transmitter IC is designed for applications in the European 868 MHz industrial-scientific-medical (ISM) band, according to the EN 300 220 telecommunications standard. It can also be used for any other system with carrier frequencies ranging from 850 MHz to 930 MHz (e.g. for applications in the US 902 to 928 MHz ISM band).
The transmitter's carrier frequency fc is determined by the frequency of the reference crystal fref. The integrated PLL synthesizer ensures that carrier frequencies, ranging from 850 MHz to 930 MHz, can be achieved. This is done by using a crystal with a reference frequency according to: fref = fc/N, where N = 32 is the PLL feedback divider ratio.
TH72035 Features and Benefits
- Fully integrated PLL-stabilized VCO
- Frequency range from 850 MHz to 930 MHz
- Single-ended RF output
- FSK through crystal pulling allows modulation from DC to 40 kbit/s
- High FSK deviation possible for wideband data transmission
- ASK achieved by on/off keying of internal power amplifier up to 40 kbit/s
- Wide power supply range from 1.95 V to 5.5 V
- Operating temperature range -40°C to +125°C
- Very low standby current
- On-chip low voltage detector
- High over-all frequency accuracy
- FSK deviation and center frequency independently adjustable
- Adjustable output power range from -11 dBm to +9 dBm
- Adjustable current consumption from 5.1 mA to 13.4 mA
- Conforms to EN 300 220 and similar standards
- 10-pin Quad Flat No-Lead 10L QFN 3x3 (Dual)
TH72035 Environmental Information
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TH72035 Frequently asked Questions
RF/sensor application advice pls
Answer
the smallest size FSK/ASK transmitters are in micro leadframe packages (MLP) measuring only 3mm x 3mm. They are:
TH72005 (290 to 350MHz),
TH72015 (380 to 450MHz),
TH72035 (850 to 930MHz).
We have seen much smaller than 100sqmm PCBs using these TXs together with a low profile SMD crystal, a small MCU etc.
TH72035 Parasitic Oscillation
Question
I am using TH72035 Transmitter 868.35MHz with a 3.3v voltage regulator(TC55RP33)The circuit is fed from a 6V Battery.Please advice how to avoid oscillation when the battery drops to about 2v.(CE Standard Requires).
/The additional filtration does not help/
Answer
the TH72035 contains an open-collector output stage. Therefore the output stage needs to be loaded at the desired operating frequency. Assuming the collector load as a RLC parallel tank, the residual load will be only resistively at resonance. Since the collector current is well controlled by the IC, the voltage swing at the collector (output) node is directly related to the real part of the load impedance. To avoid instability, the collector potential must not drop below the base potential of the output transistor, so that the output stage operates fairly in linear mode. For the TH7203X the real part of the optimum load impedance is approx. 250ohms which gives a stable operation over the whole supply range (1.9 .. 5.5V). For the TH7200X & TH7201X this is approx. 300ohms. If the lowest provided supply level guaranteed by the application can be e.g. 3V (instead of 1.9V), the available voltage swing at the output node will be higher so that the load resistance can be increased which res
Question
I use TH72035 in a remote control.
The oscillation appears during the discharging of the battery from 6V down to 0V (This test is according to the ETSI European Standard) The problem is the high internal resistance of the voltage regulator in the switching point’s area .The oscillation appears as a ripple(1-50KHz) on the VCC(voltage regulator's OUT) and this causes parasitic modulation on the carrier.
Answer
OK, so your voltage regulator is the source of oscillation. Its strong VCC ripple modulates the VCO in the TH72035. So you should better remove the root cause of the problem. Wouldn't it be easier to use just a Z-diode for voltage regulation? I don't know how you turn on and off the transmitter. If it's just by battery on/off switching, then the extra current of the Z-diode should be no problem. Otherwise you can use a bipolar tansistor and a Z-diode (at the transistor's base) for regulation.
TH71081 replacement
Answer
We can suggest following replacements:
TH72031 Transmitter - 868/915MHz, FSK (SOIC8)
TH72032 Transmitter - 868/915MHz, ASK (SOIC8)
TH72035 Transmitter - 868/915MHz, FSK/ASK (10L QFN 3x3 Dual)
For an overview of the main parameters you can download our quick section guide:
http://www.melexis.com/Asset.aspx?nID=3752
For pricing, sampling and purchasing I would like to point you to our local partner in Slovenia:
IC Elektronika d.o.o.
Vodovodna cesta 100
Ljubljana.
1000 Slovenia
Phone +386 1 5680111
Fax +386 1 5689107
E-mail prodaja@ic-elect.si
Web www.ic-elect.si
TH72035 Modulation down to DC?
Question
The information given at:-
http://www.melexis.com/ProdMain.aspx?nID=131
Suggests that TH72035 can be modulated down to DC. Is this actually possible ?
The data sheet shows in internal loop filter but no values or bandwidths are shown. I wish to modulate the RF carrier by pulling the crystal reference at around 100 to 300Hz. Can this be done?
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