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resources:eval:ad9525-user-guide [13 Feb 2013 19:12] – Loop filter design section Kyle Slightom | resources:eval:ad9525-user-guide [03 Jan 2021 22:11] (current) – fix links Robin Getz | ||
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- | ===== GENERAL DESCRIPTION | + | ====== AD9525 Evaluation Board User Guide ====== |
- | The [[adi> | + | |
- | + | ||
- | <WRAP centeralign> | + | |
- | \\ | ||
- | **Figure 1. AD9525/ | ||
- | </ | ||
- | <WRAP column 48%> | + | =====Features===== |
- | <WRAP round box> | + | |
- | // | + | |
* Simple power connection using 6 V wall adapter and on board LDO voltage regulators | * Simple power connection using 6 V wall adapter and on board LDO voltage regulators | ||
* 6 ac-coupled differential LVPECL SMA connectors | * 6 ac-coupled differential LVPECL SMA connectors | ||
Line 24: | Line 16: | ||
* Easy access to digital I/O and diagnostic signals via I/O header | * Easy access to digital I/O and diagnostic signals via I/O header | ||
* Status LEDs for diagnostic signals | * Status LEDs for diagnostic signals | ||
- | </ | ||
- | <WRAP column 48%> | + | =====Equipment Needed===== |
- | <WRAP round box> | + | * Reference oscillator or signal generator |
- | //**APPLICATIONS**// | + | * Other evaluation board to be clocked or test equipment |
- | * LTE and multicarrier GSM base stations | + | |
- | * Clocking high speed ADCs, DACs | + | |
- | * ATE and high performance instrumentation | + | * SMA cables (50 Ω) |
- | * 40 Gbps/100 Gbps OTN line side clocking | + | * 6 V wall supply (provided) |
- | * Cable/DOCSIS CMTS clocking | + | * USB cable (provided) |
- | * Test and measurement | + | |
- | \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ | + | =====Online Resources===== |
- | </WRAP></ | + | Required Software |
+ | * [[adi> | ||
+ | Documents Needed | ||
+ | * [[adi> | ||
+ | |||
+ | ===== GENERAL DESCRIPTION ===== | ||
+ | |||
+ | ---- | ||
+ | |||
+ | The [[adi> | ||
+ | |||
+ | < | ||
+ | {{: | ||
+ | \\ | ||
+ | **Figure 1. AD9525/ | ||
+ | </ | ||
===== EVALUATION BOARD HARDWARE ===== | ===== EVALUATION BOARD HARDWARE ===== | ||
+ | |||
+ | ---- | ||
+ | |||
The instructions in this section are for setting up the physical connections to the AD9525/ | The instructions in this section are for setting up the physical connections to the AD9525/ | ||
When connecting the evaluation board to a PC for the first time, you must install the evaluation software prior to connecting the evaluation board. If a previous version of the software is already installed, uninstall it before installing the latest version. | When connecting the evaluation board to a PC for the first time, you must install the evaluation software prior to connecting the evaluation board. If a previous version of the software is already installed, uninstall it before installing the latest version. | ||
- | === Power and PC Connections === | + | ==== Power and PC Connections |
- Install the AD9525 evaluation software, uninstall prior versions of the software before installation updates. Administrative privileges are required for installation. The 64-bit versions of Windows® are supported. | - Install the AD9525 evaluation software, uninstall prior versions of the software before installation updates. Administrative privileges are required for installation. The 64-bit versions of Windows® are supported. | ||
- Connect the 6V wall power supply to the main power connector labeled P500. | - Connect the 6V wall power supply to the main power connector labeled P500. | ||
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Refer to the Evaluation Board Software section for details on running the AD9525 evaluation board software. | Refer to the Evaluation Board Software section for details on running the AD9525 evaluation board software. | ||
- | === Signal Connections === | + | ==== Signal Connections |
To connect signals: | To connect signals: | ||
- Connect a signal generator to the J202 (REF A) SMA connector or to the J204 (REF B) SMA connector. By default, the reference inputs on this evaluation board are ac-coupled and terminated 50 Ω to ground. An amplitude setting of 0 dBm to 6 dBm is sufficient. | - Connect a signal generator to the J202 (REF A) SMA connector or to the J204 (REF B) SMA connector. By default, the reference inputs on this evaluation board are ac-coupled and terminated 50 Ω to ground. An amplitude setting of 0 dBm to 6 dBm is sufficient. | ||
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- SYNC_OUT can be configured as two single-ended CMOS outputs, in which case each line should be terminated with a series resistor. | - SYNC_OUT can be configured as two single-ended CMOS outputs, in which case each line should be terminated with a series resistor. | ||
- | === Bypassing the PLL (Clock Distribution Only) === | + | ==== Bypassing the PLL (Clock Distribution Only) ==== |
To bypass the PLL: | To bypass the PLL: | ||
- Connect a signal generator to the SMA connector labeled CLKIN. | - Connect a signal generator to the SMA connector labeled CLKIN. | ||
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The AD9525 default register settings configure the device as an eight output clock buffer. | The AD9525 default register settings configure the device as an eight output clock buffer. | ||
- | === Using An OFF-Board VCO/VCXO === | + | ==== Using An Off-Board VCO/ |
To use an off-board VCO or VCXO: | To use an off-board VCO or VCXO: | ||
- Remove the original VCO/VCXO or disconnect all supply voltages. (You may see coupling between the VCO/VCXO paths if two VCO/VCXOs are powered at the same time, causing pulling.) | - Remove the original VCO/VCXO or disconnect all supply voltages. (You may see coupling between the VCO/VCXO paths if two VCO/VCXOs are powered at the same time, causing pulling.) | ||
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===== LOOP FILTER DESIGN ===== | ===== LOOP FILTER DESIGN ===== | ||
+ | ---- | ||
The AD9525 PLL requires an external VCO or VCXO and a loop filter containing components tailored for a given application. The third-order passive configuration shown in Figure 2 usually results in the best performance for many applications and is the one found on the evaluation board. | The AD9525 PLL requires an external VCO or VCXO and a loop filter containing components tailored for a given application. The third-order passive configuration shown in Figure 2 usually results in the best performance for many applications and is the one found on the evaluation board. | ||
<WRAP centeralign> | <WRAP centeralign> | ||
+ | {{: | ||
\\ | \\ | ||
**Figure 2. PLL Loop Filter** | **Figure 2. PLL Loop Filter** | ||
</ | </ | ||
+ | |||
+ | The loop bandwidth of a PLL with a second-order filter (excluding R2 and C3) can be approximated using the following equation: \\ | ||
+ | <WRAP centeralign> | ||
+ | < | ||
+ | </ | ||
+ | where: \\ | ||
+ | * **// | ||
+ | * **// | ||
+ | * **//R1//** is the resistance labeled in Figure 2.\\ | ||
+ | * **// | ||
+ | |||
+ | Because **// | ||
+ | |||
+ | To determine the best loop filter for a given application, | ||
+ | |||
+ | The AD9525 evaluation board can be purchased with either a Z-Comm CRO2950B-LF external VCO or with no VCO populated. This section discusses a couple of different external VCO possibilities and their respective loop filter designs and performance. Using a high performance VCO with low phase noise allows you to create a low loop bandwidth filter to remove the jitter contained on the input reference clock. | ||
+ | |||
+ | ==== Using the Evaluation Board with a Z-Comm CRO2950B-LF VCO ==== | ||
+ | The first setup discussed is the default evaluation board configured with a Z-Comm CRO2950B-LF VCO. With the charge pump set to 1.8 mA and the feedback divider set to 24, the on-board loop filter produces a loop bandwidth of ~6 kHz and ~69° of phase margin. Table 1 shows the parameters used to attain the resulting phase noise measurements described in Figure 4. A phase noise plot of the Z-Comm CRO2950B-LF VCO is shown in Figure 3.\\ | ||
+ | <WRAP column 45%> | ||
+ | <WRAP centeralign> | ||
+ | ^ Variable | ||
+ | | VCO Operating Frequency | ||
+ | | Reference Frequency | ||
+ | | Output Frequency | ||
+ | | **// | ||
+ | | **// | ||
+ | | **// | ||
+ | | Loop Filter Bandwidth | ||
+ | | Loop Filter Phase Margin | ||
+ | **Table 1. AD9525 Evaluation Board with Z-Comm CRO2950B-LF VCO** | ||
+ | </ | ||
+ | |||
+ | <WRAP column 48%> | ||
+ | <WRAP centeralign> | ||
+ | {{: | ||
+ | \\ | ||
+ | **Figure 3. Z-Comm CRO2950B-LF VCO Phase Noise** | ||
+ | </ | ||
+ | | ||
+ | |||
+ | Table 2 displays the loop filter component values to achieve ~6 kHz bandwidth and ~69° of phase margin when operating the AD9525 as described in Table 1. Figure 4 shows the output phase noise of the AD9525 using a Z-Comm CRO2950B-LF VCO and the loop filter as defined in Table 2. | ||
+ | |||
+ | <WRAP column 45%> | ||
+ | <WRAP centeralign> | ||
+ | ^ ADIsimCLK | ||
+ | | R1 | ||
+ | | R2 | ||
+ | | C1 | ||
+ | | C2 | ||
+ | | C3 | ||
+ | |||
+ | **Table 2. AD9525 Evaluation Board Default Loop Filter Values for Z-Comm CRO2950B-LF VCO** | ||
+ | </ | ||
+ | |||
+ | <WRAP column 48%> | ||
+ | <WRAP centeralign> | ||
+ | {{: | ||
+ | |||
+ | **Figure 4. AD9525 Output Phase Noise Using Z-Comm CRO2950B-LF VCO** | ||
+ | </ | ||
+ | |||
+ | Figure 5 shows the simulated output phase noise generated by ADIsimCLK using this setup. | ||
+ | |||
+ | <WRAP centeralign> | ||
+ | {{: | ||
+ | |||
+ | **Figure 5. AD9525 ADIsimCLK Simulated Phase Noise Using Z-Comm CRO2950B-LF VCO** | ||
+ | </ | ||
+ | |||
+ | |||
+ | ==== Using the Evaluation Board with a Different VCO ==== | ||
+ | The second setup discussed uses the evaluation board with the on-board VCO and loop filter removed. Instead, this setup uses a separate VCO daughter board with a Bowei MVCO1475 VCO and a two-pole loop filter. With the charge pump set to 1.8 mA and the N divider set to 12, the loop filter was designed to give ~11 kHz of bandwidth and ~70° of phase margin. Table 3 shows the parameters used to attain the resulting phase noise measurements described in Figure 7. A phase noise plot of the Bowei MVCO1475 VCO is shown in Figure 6. | ||
+ | |||
+ | <WRAP column 45%> | ||
+ | <WRAP centeralign> | ||
+ | ^ Variable | ||
+ | | VCO Operating Frequency | ||
+ | | Reference Frequency | ||
+ | | Output Frequency | ||
+ | | **// | ||
+ | | **// | ||
+ | | **// | ||
+ | | Loop Filter Bandwidth | ||
+ | | Loop Filter Phase Margin | ||
+ | **Table 3. AD9525 Evaluation Board with Z-Comm CRO2950B-LF VCO** | ||
+ | </ | ||
+ | |||
+ | <WRAP column 48%> | ||
+ | <WRAP centeralign> | ||
+ | {{: | ||
+ | \\ | ||
+ | **Figure 6. Bowei MVCO1475 VCO Phase Noise** | ||
+ | </ | ||
+ | \\ | ||
+ | Table 4 displays the loop filter component values to achieve ~11 kHz bandwidth and ~70° of phase margin when operating the AD9525 as described in Table 1. Figure 7 shows the output phase noise of the AD9525 using a Bowei MVCO1475 and the loop filter as defined in Table 4.\\ | ||
+ | |||
+ | <WRAP column 45%> | ||
+ | <WRAP centeralign> | ||
+ | ^ ADIsimCLK | ||
+ | | R1 | ||
+ | | R2 | ||
+ | | C1 | ||
+ | | C2 | ||
+ | | C3 | ||
+ | |||
+ | **Table 4. AD9525 Evaluation Board Loop Filter Values Used with Bowei MVCO1475** | ||
+ | </ | ||
+ | <WRAP column 48%> | ||
+ | <WRAP centeralign> | ||
+ | {{: | ||
+ | \\ | ||
+ | **Figure 7. AD9525 Output Phase Noise Using Bowei MVCO1475 VCO** | ||
+ | </ | ||
+ | |||
+ | Figure 8 shows the simulated output phase noise generated by ADIsimCLK using this setup. | ||
+ | |||
+ | <WRAP centeralign> | ||
+ | {{: | ||
+ | |||
+ | **Figure 8. AD9525 ADIsimCLK Simulated Phase Noise Using Bowei MVCO1475 VCO** | ||
+ | </ | ||
+ | |||
+ | ===== EVALUATION BOARD SOFTWARE ===== | ||
+ | ---- | ||
+ | The AD9525 evaluation software allows the user to control the full functionality of the AD9525 through SPI/I2C communication on the evaluation board. | ||
+ | |||
+ | ==== Software Installation ==== | ||
+ | Do not connect the evaluation board until the software installation is complete. | ||
+ | - The latest evaluation software and documentation can be downloaded from http:// | ||
+ | - On the AD9525 Evaluation Board page, double-click AD9525Eval_Setup1.1.0.exe. (Note that the website may have a newer version.) Follow the installation instructions. | ||
+ | |||
+ | ==== Running the Software ==== | ||
+ | Power up and connect the evaluation board to the PC. See the Evaluation Board Hardware section for details on the various connectors on the evaluation board. | ||
+ | - Windows® may automatically detect the evaluation board after the board is first plugged in. Allow Windows® to install the device drivers.\\ <WRAP centeralign> | ||
+ | {{: | ||
+ | \\ | ||
+ | **Figure 9. Device Hardware Installation** | ||
+ | </ | ||
+ | - Double-click AD9525 Evaluation Software to run the AD9525 software. If the evaluation board is found by the software, AD9525 Evaluation Board in green is displayed in the lower left corner of the main window (see Figure 12). If the evaluation board was not found, No Hardware Connected! in red is displayed in the lower left corner of the window. | ||
+ | - If the evaluation board is found, proceed to the Evaluation Software Components section for details about running the software. If the evaluation board is not found, click File > Select Hardware. | ||
+ | {{: | ||
+ | \\ | ||
+ | **Figure 10. Select Hardware Window** | ||
+ | </ | ||
+ | |||
+ | AD9525 Evaluation Board in green should be displayed in the bottom left corner of the main window. Alternatively, | ||
+ | |||
+ | ===== QUICK START GUIDE TO THE AD9525 PLL ===== | ||
+ | ---- | ||
+ | The AD9525 quick start guide is intended for direct use with the AD9525/ | ||
+ | The AD9525 website contains a setup file to configure the AD9525/ | ||
+ | |||
+ | <WRAP column 48%> | ||
+ | <WRAP centeralign> | ||
+ | ^ Parameter | ||
+ | | Input Frequency | ||
+ | | Output Frequency | ||
+ | | Reference Divider | ||
+ | | Phase Detector Frequency | ||
+ | | Feedback Divider (N divider) | ||
+ | | VCO Frequency | ||
+ | | VCO Divider (M Divider) | ||
+ | | Charge Pump Current (I< | ||
+ | |||
+ | **Table 5. Example Values for Quick Start Steps** | ||
+ | </ | ||
+ | |||
+ | \\ | ||
+ | |||
+ | ==== Quick Start Steps ==== | ||
+ | When the evaluation software is installed, the evaluation board is connected, and the software is loaded, use the following steps to configure and lock the PLL. These steps assume that the input signal is present to REF A, that the evaluation board has not been modified, and that the PLL loop filter is suitable for a given application. | ||
+ | - Type the intended reference input frequency (in megahertz) in the REF A MHz box at the upper left corner of the main window and press ENTER. | ||
+ | - Type the appropriate R< | ||
+ | {{: | ||
+ | **Figure 11. Reference Inputs Block** | ||
+ | </ | ||
+ | - Program the N (feedback) divider by clicking the N text box inside of the green APLL block (see Figure 12) Type the desired value and press ENTER. For this example, N = 48 is used (see Figure 12). Note that the N divider is limited to the range of values that can be obtained by multiplying the B and P dividers. See the AD9525 data sheet for more details.\\ <WRAP centeralign> | ||
+ | {{: | ||
+ | **Figure 12. APLL Block** | ||
+ | </ | ||
+ | - Set the charge pump current multiplier (8× in this case) by clicking APLL Registers, located under the green APLL block, and selecting 8x (default) from the Charge Pump Current drop-down menu (see Figure 19). | ||
+ | - Set the VCO divider (M divider) by clicking the M text box in the green APLL block (see Figure 12). Type the preferred divide value (1 in this case) and press ENTER. Note that both the N divider and M divider make up the NTOTAL divider. The NTOTAL is detailed in the AD9525 data sheet. | ||
+ | - The output frequency of the AD9525 is then displayed in the Output Frequency box on the right side of the window.\\ <WRAP centeralign> | ||
+ | {{: | ||
+ | **Figure 13. Output Frequency Box** | ||
+ | </ | ||
+ | - Power down any unused drivers by clicking DIST REGISTERS, located under the blue OUTPUT DIST block (see Figure 14) on the right side of the main window. The Distribution window opens. | ||
+ | - Check that each output is powered off in the Power Down PECL Driver box of the Distribution window, and then click Load near the bottom of the window for these settings to be programmed into the evaluation board (see Figure 14).\\ <WRAP centeralign> | ||
+ | {{: | ||
+ | | ||
+ | **Figure 14. Output Distribution Block** | ||
+ | </ | ||
+ | - The PLL is then locked. This is indicated in the software by the small square labeled LD in the center of the green APLL block illuminating bright green (see Figure 15).\\ <WRAP centeralign> | ||
+ | {{: | ||
+ | | ||
+ | **Figure 15. Software Lock Detect Indicator** | ||
+ | </ | ||
+ | |||