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_GTS and VCCEHT_GTS rails.
| Part MPN | L (nH) | DCR (mΩ) |
|---|---|---|
| BLM18SN220TZ1 | — | 4 |
| BLM18KG260TN1 | — | 7 |
The inductors or ferrite beads in the Recommended Inductors and Ferrite Beads for the LC Filter table have been validated on Altera development kits and are for reference only. You can choose other inductors or ferrite beads according to specific applications, as long as the specification stated above can be met and the LC Filter works well. Altera recommends running the simulation to verify expected functionality.
| Part MPN | Size (mm/inch) | Temperature Characteristics | C (µF) | Tolerance | Rated Voltage (V) |
|---|---|---|---|---|---|
| GRM21BC80G107ME15 | 2012M/0805 | X6S | 100 | ±20% | 4 |
| GRM188C80G476ME01 | 1608M/0603 | X6S | 47 | ±20% | 4 |
The capacitors in the Recommended Capacitors Used for the LC Filter table have been validated on Altera development kits and are for reference only. You can choose other capacitors according to specific applications, package size changed, temperature range, form factor, and rated voltage, as long as the specification stated above can be met and the LC Filter works well. Altera recommends running the simulation to verify expected functionality.
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 7. VCCBAT Rail RC Circuit Recommendation
P0V8 (VCCL or P0V8_GR1) Filters Recommendation for Device Fabric
The following figure shows the filter recommendation for VCCPLLDIG1_HPS, VCCPLLDIG2_HPS, and VCCPLLDIG_SDM in 0.8 V group 1 power rail.
Figure 8. VCCPLLDIG1_HPS and VCCPLLDIG2_HPS LC Filter Recommendation
Figure 9. VCCPLLDIG_SDM LC Filter Recommendation
P1V8_GR2b Filters Recommendation for Device Fabric
The connections below are recommended for the VCCPLL1_HPS, VCCPLL2_HPS, VCCADC, and VCCPLL_SDM LC filter to the P1V8_GR2b voltage rails for Agilex™ 5 devices.
You can design the filter by combining or splitting these four power rails depends on PCB routing.
Figure 10. VCCPLL1_HPS and VCCPLL2_HPS LC Filter Recommendation
Figure 11. VCCADC and VCCPLL_SDM LC Filter Recommendation