Output Ferrite Beads (B1 To B4); Output Shunting Capacitors (C29 To C32); Output Inductors (L1 To L4) - Analog Devices SSM2380 User Manual

Evaluation Board User Guide

OUTPUT FERRITE BEADS (B1 TO B4)

The output beads, B1 to B4, are suggested components for
filtering out the EMI caused at the switching output nodes. The
penalty for using ferrite beads for EMI filtering is slightly worse
noise and distortion performance at the system level due to the
nonlinearity of the beads. Ensure that these beads have enough
current conducting capability while providing sufficient EMI
attenuation. The current rating needed for an 8 Ω load is approx-
imately 420 mA, and impedance at 100 MHz must be ≥120 Ω. In
addition, the lower the dc resistance (DCR) of these beads, the
better for minimizing their power consumption. Table 4
describes suggested beads.

OUTPUT SHUNTING CAPACITORS (C29 TO C32)

There are four output shunting capacitors, C29 to C32, that
work with the B1 to B4 ferrite beads or with the L1 to L4
inductors, if they are used. Use small size (0603 or 0402),
Table 4. Suggested Output Beads
Part No.
BLM18PG121SN1D
MPZ1608S101A
MPZ1608S221A
BLM18EG221SN1D
Table 5. Suggested Output Inductors
Part No.
LQM31PNR47M00
LQM31PN1R0M00
LQM21PNR47MC0
LQM21PN1R0MC0
LQH32CN2R2M53
LBC2518T2R2M
1033AS-4R7M
Manufacturer
Murata
TDK
TDK
Murata
Manufacturer
Murata
Murata
Murata
Murata
Murata
Taiyo Yuden
Toko
Rev. 0 | Page 13 of 20
multilayer ceramic capacitors that are made of X7R or C0G
(NP0) materials. Note that the capacitors can be used in pairs: a
capacitor with small capacitance (up to 100 pF) plus a capacitor
with a larger capacitance (less than 1 nF). This configuration
provides thorough EMI reduction for the entire frequency spec-
trum. Alternatively, a single capacitor of approximately 470 pF
can be used if BOM reduction is a priority.

OUTPUT INDUCTORS (L1 TO L4)

If inductors are preferred for EMI filtering at the output nodes,
choose a component value less than 2.2 µH for these inductors.
The higher the inductance, the lower the EMI is at the output;
however, the cost and power consumption by the inductors are
higher. Using 0.47 µH to 2.2 µH inductors is recommended, and
the saturation current rating must be larger than 600 mA for an
8 Ω load. Table 5 shows suggested inductors.
Z (Ω) I (mA)
MAX
120 2000
100 3000
220 2000
220 2000
L (µH) I (mA)
MAX
0.47 1400
1.0 1200
0.47 1100
1.0 800
2.2 790
2.2 630
4.7 680
UG-248
DCR (Ω) Size (mm)
0.05 1.6 × 0.8 × 0.8
0.03 1.6 × 0.8 × 0.8
0.05 1.6 × 0.8 × 0.8
0.05 1.6 × 0.8 × 0.8
DCR (Ω) Size (mm)
0.07 3.2 × 1.6 × 0.85
0.12 3.2 × 1.6 × 0.85
0.12 2.0 × 1.25 × 0.5
0.19 2.0 × 1.25 × 0.5
0.1 3.2 × 2.5 × 1.55
0.13 2.5 × 1.8 × 2
0.31 3.8 × 3.8 × 1