LMK04828B
The following figure shows the external loop filter design for LMK04828B (U2)
PLL1 and PLL2.
Figure 1. LMK04828B (U2) PLL1 and PLL2 External Loop Filter
Schematic
The following two tables identify typical U2 loop filter configurations for PLL1 in
both dual-loop and nested 0-delay modes.
| Parameter | Value |
|---|---|
| VCO Gain | 8 KHz/V |
| Loop Bandwidth | 29 Hz |
| Phase Margin | 46 deg |
| C55 (C1_LF) | 100 nF |
| C54 (C2_LF) | 680 nF |
| R58 (R2_LF) | 39 KΩ |
| Effective Charge Pump Gain | 150 uA |
| Phase Detector Frequency (MHz) | 1.25 MHz |
| External VCXO Frequency | 160 MHz |
| Parameter | Value |
|---|---|
| VCO Gain | 8 KHz/V |
| Loop Bandwidth | 21 Hz |
| Phase Margin | 50 deg |
| C55 (C1_LF) | 100 nF |
| C54 (C2_LF) | 680 nF |
| R58 (R2_LF) | 39 KΩ |
| Effective Charge Pump Gain | 1,050 uA |
| Phase Detector Frequency (MHz) | 0.08 MHz |
| External VCXO Frequency | 160 MHz |
The following table identifies a typical U2 loop filter configuration for
PLL2.
| Parameter | Value |
|---|---|
| VCO Gain | 21 MHz/V |
| Loop Bandwidth | 79 KHz |
| Phase Margin | 68 deg |
| C50 (C1_LF) | 22 pF |
| C49 (C2_LF) | 2,200 pF |
| R57 (R2_LF) | 2.7 KΩ |
| Internal Loop Filter R3 | 200 Ω |
| Internal Loop Filter C3 | 10 pF |
| Internal Loop Filter R4 | 200 Ω |
| Internal Loop Filter C4 | 10 pF |
| Effective Charge Pump Gain | 3,200 uA |
| Phase Detector Frequency (MHz) | 6.4 MHz |
| VCXO Frequency | 2,457.6 MHz |
LMX2594
The following figures show the external loop filter design for LMX2594 ADC
(U5) and DAC (U7).
Figure 2. LMX2594 ADC (U5) External Loop Filter Schematic
Figure 3. LMX2594 DAC (U7) External Loop Filter Schematic
The following table identifies a typical LMX2594 loop filter configuration.
| Parameter | Value |
|---|---|
| VCO Gain | 239 MHz/V |
| Loop Bandwidth | 32.7 kHz |
| Phase Margin | 69 deg |
| C306, C319 (C1_LF) | 2200 pF |
| C309, C318 (C2_LF) | 180 nF |
| C307, C320 (R2_LF) | 1800 pF |
| R235, R241 (R2) | 180 Ω |
| R234, R240 (R3_LF) | 180 Ω |
| Effective Charge Pump Gain | 3 mA |
| Phase Detector Frequency (MHz) | 24.576 MHz |
| VCXO Frequency | Designed for 15 GHz, but works over the whole frequency range |