Technical Note TN1203.02 XE1203 to XE1203 TrueRF™ Migration TN1203.02 Technical Note XE1203 to XE1203 TrueRFTM migration Rev 1 February 2006 www.semtech.com 1 Technical Note TN1203.02 XE1203 to XE1203 TrueRF™ Migration 1 XE1203 TRUERFTM BENEFITS • • • 2 Full FCC/ETSI compliancy without a SAW filter Unconditional stability even at 15dBm output power Improved transmission efficiency if the SAW filter is omitted (no filter insertion loss) XE1203 TRUERFTM PART NUMBERING The XE1203 TrueRF™ version part number is XE1203FI063 (and on line 3 the lot marking is PH2RT or higher, week code 0406 or higher). The ‘non TrueRF™ version part number is XE1203I063. Please contact XEMICS' technical support if in doubt. 3 PCB MIGRATION Because the XE1203 TrueRFTM is pin-compatible with the XE1203, PCB layout changes are required only if the SAW filter is omitted (substitution with an L-C filter is required). Clients deciding not to change the PCB layout can use the XE1203TrueRFTM and keep the SAW filter. 3.1 PIN NAME CHANGE Pin 11, TMOD connected to ground in the previous version of the chip becomes now VSSP (VSS for the power amplifier) connected to ground. No PCB layout modification is necessary for this. 3.2 VCO TANK The tank of the VCO can be implemented with one inductor in parallel with one capacitor, as in the previous version of the XE1203. The values for these components have to be changed when using XE1203 TrueRFTM. The characteristics of the external tank components must be as follows: Name Typical Value for 434 MHz Typical Value for 868 MHz Typical Value for 915 MHz Tolerance CV1 1.0 pF NC NC ± 5% LV1 33 nH 8.2 nH 6.8 nH ± 2% The values above are typical and may differ for different PCB layouts. For 915Mhz and 869Mhz frequency bands the use of the external capacitor CV1 should be avoided. The value of the inductor LV1 and its position (between the two footprints) should be changed to centre the VCO tuning range. Depending on the minimum supply voltage available, the VCO tuning voltage, Vlfb, should be centred as follows: Minimum supply voltage Typical Vlfb for 434 MHz Typical Vlfb for 868 MHz Typical Vlfb for 915 MHz VDDmin = 2.7V 0.9V 1.2V 1.1V VDDmin = 2.4V 0.8V 1.1V 1.0V © Semtech 2006 www.semtech.com 2 Technical Note TN1203.02 XE1203 to XE1203 TrueRF™ Migration 3.3 LOOP FILTER OF THE FREQUENCY SYNTHESIZER The loop filter of the frequency synthesizer is shown below: LFB RL1 CL2 XE1203 CL1 Figure 1. Loop filter of the frequency synthesizer. The XE1203 TrueRFTM VCO has an increased Kvco. So the loop filter components values should be changed accordingly. The values recommended for applications using bit rates up to 38.4 kbit/s are given in the table below. Name Typical Value for 434 MHz Typical Value for 868 MHz Typical Value for 915 MHz Tolerance CL1 22 nF 22 nF 22 nF ± 5% CL2 1.2 nF 1.2 nF 1.2 nF ± 5% RL1 560Ω 470Ω 470Ω ± 5% The values recommended for applications using bit rates higher than 38.4 kbit/s are given in the table below. Name Typical Value for 434 MHz Typical Value for 868 MHz Typical Value for 915 MHz Tolerance CL1 3.3 nF 4.7 nF 4.7 nF ± 5% CL2 220 pF 330 pF 330 pF ± 5% RL1 1.2 kΩ 1 kΩ 1 kΩ ± 5% © Semtech 2006 www.semtech.com 3 Technical Note TN1203.02 XE1203 to XE1203 TrueRF™ Migration 3.4 MATCHING NETWORK OF THE TRANSMITTER The optimum load impedances for 15 dBm at the three main frequencies are given in the following table. PA optimum load 434 MHz 868 MHz 915 MHz 102 – 12j 78 + 19j 83 + 18j The schematic of the recommended matching network at the output of the transmitter is given below. The two Πsections are used to provide harmonic filtering to pass FCC and ETSI regulations with sufficient margin. LT1 VDD CT2 CT3 CT1 LT2 CT4 CT5 LT3 Figure 2. Transmitter output network. The typical component values of this matching circuit are given below. Name Typical Value for 434 MHz Typical Value for 868 MHz Typical Value for 915 MHz Tolerance CT1 6.8 pF 1.5 pF 1.8 pF ± 5% CT2 1.0 pF 0.56 pF NC ± 5% CT3 22 pF 15 pF 33 pF ± 5% CT4 6.8 pF 3.3 pF 3.3 pF ± 5% CT5 4.7 pF 2.2 pF 2.2 pF ± 5% LT1 33 nH 39 nH 47 nH ± 5% LT2 22 nH 10 nH 10 nH ± 5% LT3 22 nH 8.2 nH 8.2 nH ± 5% © Semtech 2006 www.semtech.com 4 Technical Note TN1203.02 XE1203 to XE1203 TrueRF™ Migration 4 REGISTER CONFIGURATION This part of the application note describes the differences in the registers settings between the XE1203 and the XE1203 TrueRFTM. .The internally generated power-on reset sets all registers, including the test registers, to the value 00hex. When using the 1203, some peoples may have changed some test registers to improve the bit synchronizer performances. If people change to the 1203 TrueRFTM, these test registers must be set with the value 00hex which is the default value at the power-up. The following table indicates the change of configuration in the XE1203 TrueRFTM compared to the XE1203. Register Address 11101 11110 5 Register value XE1203 00011111 11000000 Register value TM 1203TrueRF 00000000 00000000 CONCLUSIONS This application note describes the necessary changes when migrating from the existing XE1203 to the XE1203TrueRFTM. PCB layout changes are necessary only when removing the SAW filter. If the SAW filter is retained then only some component values should be changed, as described above. © Semtech 2006 All rights reserved. Reproduction in whole or in part is prohibited without the prior written consent of the copyright owner. The information presented in this document does not form part of any quotation or contract, is believed to be accurate and reliable and may be changed without notice. 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