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AN RFMD® REFERENCE MANUAL RF MICRO DEVICES®, RFMD®, Optimum Technology Matching

AN RFMD® REFERENCE MANUAL RF MICRO DEVICES®, RFMD®, Optimum Technology Matching®, Enabling Wireless Connectivity™, PowerStar®, POLARIS™ TOTAL RADIO™ and UltimateBlue™ are trademarks of RFMD, LLC. BLUETOOTH is a trademark owned by Bluetooth SIG, Inc., U.S.A. and licensed for use by RFMD. All other trade names, trademarks and registered trademarks are the property of their respective owners. ©2006, RF Micro Devices, Inc. 081003 7628 Thorndike Road, Greensboro, NC 27409-9421.·For sales or technical support, contact RFMD at (+1) 336-678-5570 or sales-support@rfmd.com. 1 of 11 RF205x Calibration User Guide Integrated Configurable Components from RFMD Multi-Market Products Group RF205x Calibration User Guide RF MICRO DEVICES®, RFMD®, Optimum Technology Matching®, Enabling Wireless Connectivity™, PowerStar®, POLARIS™ TOTAL RADIO™ and UltimateBlue™ are trademarks of RFMD, LLC. BLUETOOTH is a trademark owned by Bluetooth SIG, Inc., U.S.A. and licensed for use by RFMD. All other trade names, trademarks and registered trademarks are the property of their respective owners. ©2006, RF Micro Devices, Inc. 081003 7628 Thorndike Road, Greensboro, NC 27409-9421.·For sales or technical support, contact RFMD at (+1) 336-678-5570 or sales-support@rfmd.com. 2 of 11 CONTENTS 1. Introduction ............................................................................................................................................................................................3 2. Coarse Tuning Calibration......................................................................................................................................................................4 2.1 VCO Description...................................................................................................................................................................................4 2.2 Calibration Method .............................................................................................................................................................................4 2.2.1 Calibration Enabled..............................................................................................................................................................5 2.2.2 Manual Calibration Method.................................................................................................................................................5 3. Loop Filter Calibration............................................................................................................................................................................7 3.1 VCO Gain Calibration Description ......................................................................................................................................................7 3.1.1 Setting Up the Device for VCO Gain Calibration.................................................................................................................7 3.1.2 Determining the Required Frequency Offset......................................................................................................................9 3.2 VCO Operating Frequency Compensation.........................................................................................................................................9 4. Using the Calibration Tab in the GUI....................................................................................................................................................11 RF205x Calibration User Guide RF MICRO DEVICES®, RFMD®, Optimum Technology Matching®, Enabling Wireless Connectivity™, PowerStar®, POLARIS™ TOTAL RADIO™ and UltimateBlue™ are trademarks of RFMD, LLC. BLUETOOTH is a trademark owned by Bluetooth SIG, Inc., U.S.A. and licensed for use by RFMD. All other trade names, trademarks and registered trademarks are the property of their respective owners. ©2006, RF Micro Devices, Inc. 081003 7628 Thorndike Road, Greensboro, NC 27409-9421.·For sales or technical support, contact RFMD at (+1) 336-678-5570 or sales-support@rfmd.com. 3 of 11 1. INTRODUCTION The basic philosophy behind the RF205x product family is to offer a high-linearity broadband mixer along with frequency generation capability to support a RF frequency range of approximately 50MHz to 2500MHz, and an IF frequency range of approximately 50MHz to 2500MHz. While many users of the devices will not need to cover the entire frequency range at once (for whom automatic calibration will work perfectly well), some will; this guide is aimed at those users. To reliably cover the Local Oscillator frequency range of 300MHz to 2400MHz it is necessary to calibrate the voltage controlled oscillators (VCOs) to maintain the loop bandwidth characteristics. This document explains how the different calibration mechanisms included on the chips work to achieve this. Two calibration mechanisms are provided on the chip, both can be operated either in an automatic mode or under user control. In the automatic mode operation is completely transparent to the user. The first mechanism is Coarse Tune calibration (CT Cal) designed to ensure the VCO tank circuit is tuned to the correct frequency. The second calibration mechanism is loop filter correction designed to tune out the effect of VCO tuning slope variations (KV Cal). A tab1 has been provided in the graphical user interface software provided with the evaluation board to enable users to investigate these features and perform the necessary calculations. 1 The “Calibration” tab. RF205x Calibration User Guide RF MICRO DEVICES®, RFMD®, Optimum Technology Matching®, Enabling Wireless Connectivity™, PowerStar®, POLARIS™ TOTAL RADIO™ and UltimateBlue™ are trademarks of RFMD, LLC. BLUETOOTH is a trademark owned by Bluetooth SIG, Inc., U.S.A. and licensed for use by RFMD. All other trade names, trademarks and registered trademarks are the property of their respective owners. ©2006, RF Micro Devices, Inc. 081003 7628 Thorndike Road, Greensboro, NC 27409-9421.·For sales or technical support, contact RFMD at (+1) 336-678-5570 or sales-support@rfmd.com. 4 of 11 2. COARSE TUNING CALIBRATION Coarse tuning calibration is required to ensure the VCO operates on the correct frequency. By default this calibration will occur every time the device is switched from standby into an operating mode. 2.1 VCO DESCRIPTION The on-chip VCO actually consists of three separate VCOs covering the following ranges2: VCO# Frequency range (approx) VCO1 (VCOSEL = 0) 1800MHz to 2500MHz VCO2 (VCOSEL = 1) 1500MHz to 2100MHz VCO3 (VCOSEL = 2) 1150MHz to 1650MHz3 The user must select the correct VCO for the frequency of operation, this task is not performed automatically by the chip but must be programmed into PLL1x0 and/or PLL2x0 registers4. It should also be remembered that the oscillation frequency of VCO3 is determined by an external inductor and is therefore subject to change depending on the PCB layout. To keep the tuning sensitivity of the VCOs within an acceptable range, each VCO has a series of switched capacitors (see figure below) which are used to set the oscillating frequency of the VCO to approximately the right value. This task is performed automatically if the CT calibration enable bits are set5; however, there is a small time penalty introduced, approximately 1500 phase detector clock cycles (50us to 60us at 26MHz phase detector frequency), into the frequency switching time to accomplish this task. 1 2 4 8 16 32 64 FM demod Tuning cap control P2_CT_DEF Figure 1. VCO Coarse Tuning 2.2 CALIBRATION METHOD For the sake of simplicity, the following description will refer to the Path2 registers, but the same will apply to the Path1 if that is used. 2 The tuning range of each VCO is approximately +/-20% out of which some allowance has to be made for temperature effects. 3 The tuning range of VCO3 depends on the external inductor value, the figures are taken from the RF2051 applications board. 4 P1_VCOSEL and/or P2_VCOSEL respectively 5 P1_CT_EN in PLL1x0 and P2_CT_EN in PLL2x0 RF205x Calibration User Guide RF MICRO DEVICES®, RFMD®, Optimum Technology Matching®, Enabling Wireless Connectivity™, PowerStar®, POLARIS™ TOTAL RADIO™ and UltimateBlue™ are trademarks of RFMD, LLC. BLUETOOTH is a trademark owned by Bluetooth SIG, Inc., U.S.A. and licensed for use by RFMD. All other trade names, trademarks and registered trademarks are the property of their respective owners. ©2006, RF Micro Devices, Inc. 081003 7628 Thorndike Road, Greensboro, NC 27409-9421.·For sales or technical support, contact RFMD at (+1) 336-678-5570 or sales-support@rfmd.com. 5 of 11 2.2.1 Calibration Enabled Automatic calibration is performed when the P2_CT_EN bits are set to 11 in the PLL2x0 register. A calibration is performed whenever the device is switched from standby to an active mode. The calibration mechanism uses a frequency-locked loop to switch the VCO capacitors to bring the varactor control voltage close to a predetermined level. This level is determined by the contents of P2_CT_V in the PLL2x5 register; the value is set to 1000 by default, ie mid-rail. Changing this value is not recommended without a careful analysis of the stability of the circuit operation with temperature, etc. Figure 2. Coarse Tuning Autocalibration Flow 2.2.2 Manual Calibration Method If P2_CT_EN is set to 00 then the user will have to load the correct coarse tune values into the P2_CT_DEF register when the frequency or VCO are changed. The following graph shows a typical variation of CT_DEF with frequency across the tuning range of the VCOs. Since the P2_CT_DEF value changes when the frequency changes, if the VCO frequency is altered by more than a few MHz (the exact frequency being dependant on the VCO operating frequency) it would be advisable to program a new P2_CT_DEF value. From the graph it can be seen that for VCO2 the CT_CAL value varies from 0-127 over a frequency range of approximately 1400MHz to 2200MHz, corresponding to a change of CT_VAL every 6MHz on average. RF205x Calibration User Guide RF MICRO DEVICES®, RFMD®, Optimum Technology Matching®, Enabling Wireless Connectivity™, PowerStar®, POLARIS™ TOTAL RADIO™ and UltimateBlue™ are trademarks of RFMD, LLC. BLUETOOTH is a trademark owned by Bluetooth SIG, Inc., U.S.A. and licensed for use by RFMD. All other trade names, trademarks and registered trademarks are the property of their respective owners. ©2006, RF Micro Devices, Inc. 081003 7628 Thorndike Road, Greensboro, NC 27409-9421.·For sales or technical support, contact RFMD at (+1) 336-678-5570 or sales-support@rfmd.com. 6 of 11 Set Path2 LO freq. P2_CT_EN = 0 P2_CT_DEF = x Standby Enable device Operation Determine the coarse tune (P2_CT_DEF) value Figure 3. Coarse Tuning Manual Calibration For a given value of P2_CT_DEF the varactor on the control input of the VCO will tune it by ±15MHz, again depending on the operating frequency and the choice of active or passive loop filter. The easiest way to determine the required values for P2_CT_DEF is to perform an automatic calibration; once for a suitable number of frequencies, then to store the resulting values for later use. Since the curve is smooth it will be possible to perform an interpolation between frequency points to reduce the amount of storage required for the calibration data. Figure 4. CT_CAL versus VCO Frequency (measured on RF2051 applications board at room temperature) RF205x Calibration User Guide RF MICRO DEVICES®, RFMD®, Optimum Technology Matching®, Enabling Wireless Connectivity™, PowerStar®, POLARIS™ TOTAL RADIO™ and UltimateBlue™ uploads/s3/ rf205x-calibration-user-guide.pdf