EVB7108B-868-FSK-A

EVB7108B-868-FSK-A Datasheet

EVB7108

Part	Datasheet
EVB7108B-868-FSK-A	EVB7108B-868-FSK-A (pdf)

Related Parts	Information
EVB7108A-915-FSK-A	EVB7108A-915-FSK-A

PDF Datasheet Preview
EVB7108 868/915MHz Transmitter Evaluation Board Description The TH7108 antenna board is designed to optimally match the differential power amplifier output to a loop antenna. The TH7108 can be populated either for FSK, ASK or FM transmission. The default population is for FSK or ASK transmission. Adding a varactor diode can easily be done in order to modify the circuit for analog FM. The evaluation board contains a differential-drive loop antenna printed on the PCB Printed Circuit Board . The size of the loop antenna is matched to the resonant frequency. Board layout data in Gerber format is available on request. ! Fully integrated, PLL-stabilized VCO ! Flexible frequency range from 850 MHz to 930 MHz ! FSK through crystal pulling allows modulation from DC to 20 kbit/s ! High deviation possible for wideband data transmission ! 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 equivalent radiated power ERP range from -20 dBm to -6 dBm ! Adjustable current consumption from mA to mA ! Frequency deviation and center frequency independently adjustable ! Differential output well-suited for loop antenna ! External clock available for µC drive, down to V supply ! ”Clock only” mode ! Conforms to EN 300 220 standard Ordering Information Part No. EVB7108-868-FSK EVB7108-868-ASK EVB7108-915-FSK EVB7108-915-ASK ! Keyless car and central locking ! Low-power telemetry ! Alarm and security systems ! General digital data transmission ! General analog audio signal transmission 1 of 8 EVB Description Aug/02 EVB7108 868/915MHz Transmitter Evaluation Board Description Theory of Operation General As depicted in Fig.1, the TH7108 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 RPS or by varying the voltage VPS at pin PS. The open-collector differential output OUT1, OUT2 can be used to either directly drive a loop antenna or to be converted to a singleended impedance by means of a balanced-tounbalanced 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. FSK Modulation A Colpitts crystal oscillator XOSC is used as the reference oscillator of a phase-locked loop PLL synthesizer. FSK modulation is achieved by pulling the crystal XTAL through the data. So a CMOScompatible data stream applied at input DATA digitally modulates the XOSC. Two external pulling capacitors CX1 and CX2 allow the FSK deviation and center frequency to be adjusted independently. At DATA = LOW CX2 is connected in parallel to CX1 leading to the low-frequency component of the FSK spectrum fmin while at DATA = HIGH CX2 is deactivated and the XOSC is set to its high frequency, leading to fmax. An external reference signal can be directly ACcoupled to pin RO1. Then the TH7108 is used without an XTAL. The reference signal has to contain the FSK or FM and sets the carrier frequency. 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. ASK Modulation The TH7108 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. Mode Control Logic The mode control logic allows four different modes of operation as listed in the following table. The mode control pins ENCK and ENTX are pulleddown internally. This guarantees that the whole circuit is shut down if these pins are left floating. The clock output CKOUT can be used to drive a µC. This output can be activated by the ENCK pin as required for any specific application. Clock frequency is 1/8 of the reference crystal frequency. The clock output is slew-rate limited in order to keep spurious signal emission as low as possible. The voltage swing at CKOUT depends on the capacitive loading at this pin. It is approx. 2 Vpp at Cload = 5 pF. ENCK ENTX Mode 0 all OFF whole circuit in standby 1 TX only TX functionality only, no clock available 0 clock TX in standby and clock only available 1 all ON TX functional and clock available Table 1 Modes of operation 2 of 8 EVB Description Aug/02 Block Diagram EVB7108 868/915MHz Transmitter Evaluation Board Description VEE 14 OUT1 13 OUT2 12 VEE 11 ENCK 7 ENTX 6 16 LF2 2 SUB CF2 VCO mode control RPS PS 9 PFD charge pump VCC 15 1 LF1 CF1 RF1 div32 XOSC VCC 10 3 DATA div 8

PDF Datasheet Preview

EVB7108
868/915MHz Transmitter Evaluation Board Description

The TH7108 antenna board is designed to optimally match the differential power amplifier output to a loop antenna. The TH7108 can be populated either for FSK, ASK or FM transmission. The default population is for FSK or ASK transmission. Adding a varactor diode can
easily be done in order to modify the circuit for analog FM. The evaluation board contains a differential-drive loop antenna printed on the PCB Printed Circuit Board . The size of the loop antenna is matched to the resonant frequency.

Board layout data in Gerber format is available on request.
! Fully integrated, PLL-stabilized VCO ! Flexible frequency range from
850 MHz to 930 MHz ! FSK through crystal pulling allows modulation
from DC to 20 kbit/s ! High deviation possible for wideband data
transmission ! 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 equivalent radiated power ERP
range from -20 dBm to -6 dBm ! Adjustable current consumption from
mA to mA ! Frequency deviation and center frequency
independently adjustable ! Differential output well-suited for loop antenna ! External clock available for µC drive,
down to V supply ! ”Clock only” mode ! Conforms to EN 300 220 standard
Ordering Information Part No.

EVB7108-868-FSK EVB7108-868-ASK

EVB7108-915-FSK EVB7108-915-ASK
! Keyless car and central locking ! Low-power telemetry ! Alarm and security systems
! General digital data transmission ! General analog audio signal transmission
1 of 8

EVB Description Aug/02

EVB7108
868/915MHz Transmitter Evaluation Board Description

Theory of Operation

General As depicted in Fig.1, the TH7108 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 RPS or by varying the voltage VPS at pin PS. The open-collector differential output OUT1, OUT2 can be used to either directly drive a loop antenna or to be converted to a singleended impedance by means of a balanced-tounbalanced 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.

FSK Modulation A Colpitts crystal oscillator XOSC is used as the reference oscillator of a phase-locked loop PLL synthesizer. FSK modulation is achieved by pulling the crystal XTAL through the data. So a CMOScompatible data stream applied at input DATA digitally modulates the XOSC. Two external pulling capacitors CX1 and CX2 allow the FSK deviation and center frequency to be adjusted independently. At DATA = LOW CX2 is connected in parallel to CX1 leading to the low-frequency component of the FSK spectrum fmin while at DATA = HIGH CX2 is deactivated and the XOSC is set to its high frequency, leading to fmax. An external reference signal can be directly ACcoupled to pin RO1. Then the TH7108 is used without an XTAL. The reference signal has to contain the FSK or FM and sets the carrier frequency.

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.

ASK Modulation The TH7108 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.

Mode Control Logic The mode control logic allows four different modes of operation as listed in the following table. The mode control pins ENCK and ENTX are pulleddown internally. This guarantees that the whole circuit is shut down if these pins are left floating. The clock output CKOUT can be used to drive a µC. This output can be activated by the ENCK pin as required for any specific application. Clock frequency is 1/8 of the reference crystal frequency. The clock output is slew-rate limited in order to keep spurious signal emission as low as possible. The voltage swing at CKOUT depends on the capacitive loading at this pin. It is approx. 2 Vpp at Cload = 5 pF.

ENCK ENTX Mode
0 all OFF whole circuit in standby
1 TX only TX functionality only, no
clock available
0 clock TX in standby and clock
only available
1 all ON TX functional and clock
available

Table 1 Modes of operation
2 of 8

EVB Description Aug/02

Block Diagram

EVB7108
868/915MHz Transmitter Evaluation Board Description

VEE 14 OUT1 13 OUT2 12 VEE 11 ENCK 7 ENTX 6
16 LF2 2 SUB CF2

VCO mode control

RPS PS 9

PFD charge pump

VCC 15
1 LF1 CF1 RF1
div32

XOSC

VCC 10
3 DATA
div 8

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Datasheet ID: EVB7108B-868-FSK-A 647776