EVB7108A-915-FSK-A

EVB7108 868/915MHz Transmitter Evaluation Board Description General Description 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. 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 Board layout data in Gerber format is available on request. Features ! Adjustable equivalent radiated power (ERP) range from -20 dBm to -6 dBm ! Adjustable current consumption from 6.2 mA to 12.5 mA ! Frequency deviation and center frequency independently adjustable ! Differential output well-suited for loop antenna ! External clock available for µC drive, down to 1.9 V supply ! ”Clock only” mode ! Conforms to EN 300 220 standard ! 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 2.2 V to 5.5 V ! High over-all frequency accuracy ! Very low standby current Ordering Information Part No. EVB7108-868-FSK EVB7108-868-ASK EVB7108-915-FSK EVB7108-915-ASK Applications ! General digital data transmission ! General analog audio signal transmission ! Keyless car and central locking ! Low-power telemetry ! Alarm and security systems 390120710801 Rev. 007 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 = –15 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 kΩ. Bandgap biasing ensures stable operation of the IC at a power supply range of 2.2 V to 5.5 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 Description 0 0 all OFF whole circuit in standby 0 1 TX only TX functionality only, no clock available 1 0 clock only 1 1 all ON TX functional and clock available TX in standby and clock available Table 1: Modes of operation For more detailed information, please refer to the latest TH7108 data sheet revision. 390120710801 Rev. 007 2 of 8 EVB Description Aug/02 EVB7108 868/915MHz Transmitter Evaluation Board Description ENTX 6 ENCK 7 VEE 11 OUT2 12 OUT1 13 2 SUB CF2 RF1 CF1 LF1 3 DATA CX1 4 CX2 XTAL RO2 5 RO1 8 div 8 CKOUT VCC 10 XOSC 1 PFD div32 charge pump VCC 15 16 LF2 VCO PS 9 PA mode control RPS VEE 14 VCC Block Diagram Fig. 1: TH7108 block diagram with external components 390120710801 Rev. 007 3 of 8 EVB Description Aug/02 EVB7108 868/915MHz Transmitter Evaluation Board Description Circuit Diagram C2 C1 L2 L1 C3 C4 PS CKOUT XTAL RF1 R3 CX3 CF2 8 ENCK 7 ENTX 6 RO1 5 4 RO2 3 DATA SUB 2 1 LF1 RF2 CX2 9 10 VCC VEE OUT2 11 12 13 OUT1 14 VEE 15 VCC LF2 16 RPS CX1 CF1 V1 R1 R2 390120710801 Rev. 007 4 of 8 1 2 CKOUT GND 1 2 3 VCC ENCK GND 1 2 ENTX VCC 1 2 FM/ASK GND 1 2 FSK GND 1 2 VCC GND C5 EVB Description Aug/02 EVB7108 868/915MHz Transmitter Evaluation Board Description PCB Top View C2 C1 L1 L2 C3 C4 RPS 9 RF2 16 R3 TH7108 8 1 CX2 RF1 CF1 CF2 CX1 Cx3 R1 V1 R2 C5 XTAL GND CKOUT GND ENCK 1 VCC VCC 1 ENTX GND 1 FM/ASK GND GND VCC 1 FSK 1 1 Board size is 34mm x 44mm Board Connection VCC FSK FM/ASK CKOUT Power supply (2.2 V to 5.5 V) Input for FSK data (CMOS) Input for FM signal (analog) or ASK data (CMOS) Clock output (3.4 MHz) 390120710801 Rev. 007 5 of 8 ENCK ENTX GND Mode control pin (see table 1) Mode control pin (see table 1) Several ground pins EVB Description Aug/02 EVB7108 868/915MHz Transmitter Evaluation Board Description Board Component Values Part Size Value 868.3 MHz Value 915 MHz Tolerance CF1 0805 5.6 nF 4.7 nF ±10% loop filter capacitor CF2 0805 27 pF 27 pF ±10% loop filter capacitor ±5% XOSC capacitor for FSK (∆f = ±30 kHz) XOSC capacitor for ASK, trimmed to fC Description CX1_FSK 0603 56 pF 56 pF CX1_ASK 0603 18 pF 18 pF ±5% CX2 0603 1 nF 1 nF ±5% XOSC capacitor, only needed for FSK CX3 0603 1 nF 1 nF ±10% XOSC capacitor, only needed for FM C1 1206 2.2 pF 2.2 pF ±2% antenna resonance capacitor C2 0805 1.2 pF 1 pF ±2% antenna resonance capacitor C3 0603 330 pF 330 pF ±10% blocking capacitor C4 0603 330 pF 330 pF ±10% blocking capacitor C5 1206 220 nF 220 nF ±20% blocking capacitor L1 0603 150 nH 150 nH ±10% biasing inductor L2 0603 150 nH 150 nH ±10% biasing inductor RF1 0805 1.6 kΩ 1.6 kΩ ±10% loop filter resistor RF2 0805 2.0 kΩ 2.0 kΩ ±10% loop filter resistor RPS 0805 47 kΩ 47 kΩ ±10% power-select resistor R1 0805 470 kΩ 470 kΩ ±10% optional pull-up resistor, typically not needed R2 0805 30 kΩ 30 kΩ ±10% varactor bias resistor, only needed for FM R3 0805 0Ω ±10% ASK jumper, only needed for ASK V1 XTAL SOD323 HC49/S 0Ω BB535 27.1344 MHz fundamental wave 28.5938 MHz fundamental wave PCB loop antenna PCB loop antenna PCB loop antenna long side length 18 mm 18 mm on FR4 PCB material side length including length of C1 and C2 small side length 9 mm 9 mm on FR4 PCB material Line width 2 mm 2 mm on FR4 PCB material ±30ppm calibration ±30ppm temp. varactor diode, only needed for FM crystal, Cload = 12 pF to 15 pF, C0, max = 7 pF, Rm, max = 40 Ω The listed component values are default values. All values might be changed to fit to any specific application. As for example FSK deviation can be set by varying CX1 and CX2, output power at FSK/FM transmission can be changed through RPS or through RPS and R3 at ASK transmission, respectively. Pads for C1 are for population of a fixed-value capacitor with size 1206 or a to use trimming capacitor either. 390120710801 Rev. 007 6 of 8 EVB Description Aug/02 EVB7108 868/915MHz Transmitter Evaluation Board Description Package Information E1 E 1 2 3 D α A1 A L b e Fig. 2: QSOP16 all Dimension in mm, coplanarity < 0.1mm D E1 E A A1 e b L α min 4.80 3.81 5.79 1.35 0.10 0.635 0.20 0.40 0° max 4.98 3.99 6.20 1.75 0.25 0.30 1.27 8° all Dimension in inch, coplanarity < 0.004” 390120710801 Rev. 007 min 0.189 0.150 0.228 0.0532 0.0040 0.025 0.008 0.016 0° max 0.196 0.157 0.244 0.0688 0.0098 0.012 0.050 8° 7 of 8 EVB Description Aug/02 EVB7108 868/915MHz Transmitter Evaluation Board Description Disclaimer Devices sold by Melexis are covered by the warranty and patent indemnification provisions appearing in its Term of Sale. Melexis makes no warranty, express, statutory, implied, or by description regarding the information set forth herein or regarding the freedom of the described devices from patent infringement. Melexis reserves the right to change specifications and prices at any time and without notice. Therefore, prior to designing this product into a system, it is necessary to check with Melexis for current information. This product is intended for use in normal commercial applications. Applications requiring extended temperature range, unusual environmental requirements, or high reliability applications, such as military, medical lifesupport or life-sustaining equipment are specifically not recommended without additional processing by Melexis for each application. The information furnished by Melexis is believed to be correct and accurate. However, Melexis shall not be liable to recipient or any third party for any damages, including but not limited to personal injury, property damage, loss of profits, loss of use, interrupt of business or indirect, special incidental or consequential damages, of any kind, in connection with or arising out of the furnishing, performance or use of the technical data herein. No obligation or liability to recipient or any third party shall arise or flow out of Melexis’ rendering of technical or other services. © 2002 Melexis NV. All rights reserved. For the latest version of this document. Go to our website at www.melexis.com Or for additional information contact Melexis Direct: Europe and Japan: All other locations: Phone: +32 1367 0495 E-mail: sales_europe@melexis.com Phone: +1 603 223 2362 E-mail: sales_usa@melexis.com QS9000, VDA6.1 and ISO14001 Certified 390120710801 Rev. 007 8 of 8 EVB Description Aug/02