4. Board LC Recommended Filters for Noise Reduction in Combined Power Delivery Rails
The part numbers of ferrite bead (FB) and inductances (L) selected in this chapter are the parts which are recommended by Altera. However, you can select different part numbers as long as the inductance/impedance at certain frequency, resistance, and other parameters of the new parts are similar to recommended FB/L part (similar inductance/impedance and similar to lower resistance within frequency range mentioned in the data sheet of recommended part).
CAUTION:
Any sense line used on board must be placed before LC filter. If the sense line is placed after the LC filter, this results in a serious oscillation to the rails and unstable voltage that is an input to the voltage regulator feedback pin function.
Note: If the power rail is using LDO, you do not need to use the LC filter.
If you are using the recommended switching voltage regulator (LTC7151S), with a proper design from ADI, and meet the simulated 5 mV ripple specification, you do not need to use the LC filter for VCCERT_FGT_GXF, VCCERT1_FHT_GXF, and VCCRT_GXR rails.
| Part MPN | L (nH) | DCR (mΩ) |
|---|---|---|
| SL1616A-R10MHF | 100 | 0.32 |
| SL1616A-R05MHF | 50 | 0.32 |
| BLM18SN220TZ1 | — | 4 |
| BLM18KG260TN1 | — | 7 |
The inductors or ferrite beads listed in the table above have been validated on the Altera development kits and should be used as a reference only. You can choose other inductors or ferrite beads according to specific applications, as long as the specifications stated above are met and the LC filter works well. Altera recommends you to run the simulation to ensure there is no further changes.
| Part MPN | Size (mm/inch) | Temperature Character | Capacitor Value (µF) | Capacitor Tolerance (%) | Rated Voltage (V) |
|---|---|---|---|---|---|
| GRM21BC80G107ME15 | 2012M/0805 | X6S | 100 | ±20 | 4 |
| GRM21BC80G476ME15 | 2012M/0805 | X6S | 47 | ±20 | 4 |
| GRM21BC81C226ME44 | 2012M/0805 | X6S | 22 | ±20 | 16 |
| GRM188C80G476ME01 | 1608M/0603 | X6S | 47 | ±20 | 4 |
The capacitors listed in the table above have been validated on the Altera development kits and should be used as a reference only. You can choose other capacitors according to specific applications, package size used, temperature range, form factor, and rated voltage, as long as the specifications stated above are met and the LC filter works well. Altera recommends you to run the simulation to ensure there is no further changes.
Choosing the LC Filter based on the DCR Value
DC drop specification must be around 0.5% of the voltage supply. If the voltage rail is 0.9 V, current is 1 A, BLM18SN220TZ1 DCR is 4 mΩ, DC drop = current x DCR = 1 A x 4 mΩ = 4 mV. The 0.5% specification of 0.9 V is 4.5 mV, which is within the specification. For a higher current value, SL1616 is the most suitable as it has lowest DCR.
VCCBAT RC Circuit Using the Device Security AES BBRAM Key
The connection shown below is recommended for the VCCBAT. Connect this pin to a non-volatile battery power source in the range of 1.0 V to 1.8 V. A series RC (R=10 KΩ, C=1 µF) circuit must be added to the VCCBAT rail.
Figure 8. VCCBAT Rail RC Circuit Recommendation
P1V8_GR2 ( Agilex™ 7 F-Series and I-Series)/P1V8_GR3 ( Agilex™ 7 M-Series) Filters Recommendation for Device Fabric
The connections below are recommended for the P1V8_GR2_FLTR voltage rails for the Agilex™ 7 F-Series and I-Series devices or the P1V8_GR3_FLTR voltage rails for the Agilex™ 7 M-Series devices for noise filtering. The P1V8_GR2_FLTR for the Agilex™ 7 F-Series and I-Series devices or the P1V8_GR3_FLTR for the Agilex™ 7 M-Series devices consists of VCCADC, VCCPLL_SDM, and VCCPLL_HPS.
Figure 9. VCCADC, VCCPLL_SDM, and VCCPLL_HPS Filter Recommendation
Figure 10. VCCPLL_NOC LC Filter Recommendation
P1V2_GR3 Filters Recommendation for Device Fabric
The following figure shows the filter recommendation for VCCA_PLL in 1.2 V VCCIO power rail.
Figure 11. VCCA_PLL Filter Recommendation
Figure 12. VCCA_PLL LC Filter Recommendation (Low Power Scenario)
P0V8_GR1 Filters Recommendation for Device Fabric
The following figure shows the filter recommendation for the VCCPLLDIG_SDM, VCCPLL_NOC, and VCCPLLDIG_NOC in P0V8_GR1 power rail.
Figure 13. VCCPLLDIG_SDM Filter Recommendation
Figure 14. VCCLPLL_NOC LC Filter Recommendation
Figure 15. VCCPLLDIG_NOC LC Filter Recommendation
VCCL Filters Recommendation for Device Fabric
The following figure shows the filter recommendation for the VCCPLLDIG_HPS in VCCL power rail.
Figure 16. VCCPLLDIG_HPS Filter Recommendation