TH71081EDC

TH71081EDC Datasheet

TH71081

Part	Datasheet
TH71081EDC	TH71081EDC (pdf)

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TH71081 868/915MHz ASK Transmitter / LO Source ! Fully integrated, PLL-stabilized VCO ! Flexible frequency range from 800 MHz to 930 MHz ! ASK achieved by on/off keying of internal power amplifier ! FM possible with external varactor ! Wide power supply range from V to V ! High over-all frequency accuracy ! Very low standby current ! Adjustable output power range from -15 dBm to +1 dBm ! Adjustable current consumption from mA to mA ! Differential output well-suited for loop antenna ! Conforms to EN 300 220 and similar standard Ordering Information Part No. TH71081 Temperature Range -40 C° to 85 °C Package SOIC8 Application Examples ! Keyless car and central locking ! Low-power telemetry ! Alarm and security systems ! General digital data transmission ! General analog audio signal transmission ! Local oscillator signal generation Pin Description LF 1 RO 2 ENTX 3 PS/DATA 4 TH71081 8 VEE 7 OUT1 6 OUT2 5 VCC Page 1 of 10 Data Sheet Dec. 2001 TH71081 868/915MHz ASK Transmitter / LO Source The TH71081 ASK transmitter IC is designed for applications in the European 868MHz industrialscientific-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 800 MHz to 930 MHz e.g. for applications in the US 915MHz ISM band . The transmitter's carrier frequency fc is determined by the frequency of the reference crystal fref that is used. The integrated PLL synthesizer ensures that each RF value, ranging from 800 MHz to 930 MHz, can be achieved by using a crystal with reference frequency according to fref = fc/N, where N = 32 is the PLL feedback divider ratio. Theory of Operation General As depicted in Fig.1, the TH71081 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. An external loop filter at pin LF determines the dynamic behaviour of the PLL and suppresses reference spurious signals. The VCO’s output signal feeds the power amplifier PA . RF signal power Po can be adjusted in six steps from Po = dBm to +1 dBm either by changing the value of resistor R1 or by varying the voltage VPS at pin PS/DATA. The open-collector differential output OUT1, OUT2 can be used to either directly drive a loop antenna or to be converted to a single-ended impedance by means of a balanced-to-unbalanced balun transformer. For maximum available output power, the differential output should be matched to a load of approx. 1 Bandgap biasing ensures stable operation of the IC at a power supply range of V to V. ASK Modulation The TH71081 can be ASK-modulated by applying data directly at pin PS. This turns the PA on and off and therefore leads to an ASK signal at the output. LO Source Many applications require a stable RF source. For this purpose, the TH71081 can be used without modulation as an easy-to-use, PLL-stabilized, continuous wave CW generator. Frequency Modulation FM For FM operation an external varactor is required. It simply acts as a pulling capacitor connected in series to the crystal. Then the analog modulation signal, applied through a series resistor, directly modulates the XOSC. Mode Control Logic The mode control logic allows two different modes of operation as listed in the following table. The mode control pin ENTX is pulled-down internally. This guarantees that the whole circuit is shut down if this pin is left floating. ENTX Mode 0 TX disabled whole circuit in standby 1 TX enable TX active Table 1 Modes of operation Page 2 of 10 Data Sheet Dec. 2001 Block Diagram TH71081 868/915MHz ASK Transmitter / LO Source OUT1 7 OUT2 6 ENTX 3 PA VCO mode control PS/DATA 4 8 VEE charge pump VCC 5 LF 1 CF1 CF2 RF1

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TH71081
868/915MHz ASK Transmitter / LO Source
! Fully integrated, PLL-stabilized VCO ! Flexible frequency range from 800 MHz to 930 MHz ! ASK achieved by on/off keying of internal
power amplifier ! FM possible with external varactor ! Wide power supply range from V to V ! High over-all frequency accuracy ! Very low standby current
! Adjustable output power range from -15 dBm to +1 dBm
! Adjustable current consumption from mA to mA
! Differential output well-suited for loop antenna
! Conforms to EN 300 220 and similar standard
Ordering Information Part No.

TH71081

Temperature Range -40 C° to 85 °C

Package SOIC8

Application Examples
! Keyless car and central locking ! Low-power telemetry ! Alarm and security systems ! General digital data transmission ! General analog audio signal transmission ! Local oscillator signal generation

Pin Description

LF 1 RO 2 ENTX 3 PS/DATA 4

TH71081
8 VEE 7 OUT1 6 OUT2 5 VCC

Page 1 of 10

Data Sheet Dec. 2001

TH71081
868/915MHz ASK Transmitter / LO Source

The TH71081 ASK transmitter IC is designed for applications in the European 868MHz industrialscientific-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 800 MHz to 930 MHz e.g. for applications in the US 915MHz ISM band .

The transmitter's carrier frequency fc is determined by the frequency of the reference crystal fref that is used. The integrated PLL synthesizer ensures that each RF value, ranging from 800 MHz to 930 MHz, can be achieved by using a crystal with reference frequency according to fref = fc/N, where N = 32 is the PLL feedback divider ratio.

Theory of Operation

General As depicted in Fig.1, the TH71081 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. An external loop filter at pin LF determines the dynamic behaviour of the PLL and suppresses reference spurious signals. The VCO’s output signal feeds the power amplifier PA . RF signal power Po can be adjusted in six steps from Po = dBm to +1 dBm either by changing the value of resistor R1 or by varying the voltage VPS at pin PS/DATA. The open-collector differential output OUT1, OUT2 can be used to either directly drive a loop antenna or to be converted to a single-ended impedance by means of a balanced-to-unbalanced balun transformer. For maximum available output power, the differential output should be matched to a load of approx. 1 Bandgap biasing ensures stable operation of the IC at a power supply range of V to V.

ASK Modulation The TH71081 can be ASK-modulated by applying data directly at pin PS. This turns the PA on and off and therefore leads to an ASK signal at the output.

LO Source Many applications require a stable RF source. For this purpose, the TH71081 can be used without modulation as an easy-to-use, PLL-stabilized, continuous wave CW generator.

Frequency Modulation FM For FM operation an external varactor is required. It simply acts as a pulling capacitor connected in series to the crystal. Then the analog modulation signal, applied through a series resistor, directly modulates the XOSC.

Mode Control Logic The mode control logic allows two different modes of operation as listed in the following table. The mode control pin ENTX is pulled-down internally. This guarantees that the whole circuit is shut down if this pin is left floating.

ENTX

Mode
0 TX disabled whole circuit in standby
1 TX enable TX active

Table 1 Modes of operation

Page 2 of 10

Data Sheet Dec. 2001

Block Diagram

TH71081
868/915MHz ASK Transmitter / LO Source

OUT1 7 OUT2 6 ENTX 3

PA VCO
mode control

PS/DATA 4
8 VEE
charge pump

VCC 5

LF 1 CF1

CF2 RF1

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Datasheet ID: TH71081EDC 647811