SMD Ferrite Selection

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Harry Terence Hopkins
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1 SMD Ferrite Selection lex Snijder Field pplication Engineer Wurth Electronik Nederland BV December 2014 LED EVENT s-hertogenbosch

2 GEND What is a Chip Bead? CBF Details Losses Calculations Selecting the right Chip Bead Tooling (demo) if we have time Otherwise visit our stand 2

3 The Würth Group strong family 3

4 The Würth Elektronik Group 4

5 Globally available. Locally present. 5

CBF DETILS Passive device It s just an inductor Removal of unwanted

ground planes, and data signals Removes noise energy in form of

destroyed, only converted Frequency dependant K (lso Known s)

6 CBF DETILS Passive device It s just an inductor Removal of unwanted noise at high frequencies for a PCB solution Supply voltage lines, ground planes, and data signals Removes noise energy in form of heat law of conservation of energy Energy cannot be created nor destroyed, only converted Frequency dependant K (lso Known s) frequency dependent resistor Material specific Material must be non conductive 6

7 CBF DETILS General use High frequency 7

8 LOSSES Inductors 1. pplication: Storage inductor 1. Request: Lowest possible core losses at switching frequency (HIGH Q) /May/2012 V2 MSz Confidential Ferrite Selection TBD Ferrite Q = X R L 2. pplication: bsorber / Filter 1. Request: Highest possible core losses at application frequency (LOW Q) 8

Effect of impedance in high speed signal line 90 Ohm @ 100 MHz C.M 18 Ohm @ 240 MHz D.M. 600 Ohm @ 100 MHz C.

9 Effect of impedance in high speed signal line MHz C.M MHz D.M MHz C. M MHz D.M MHz Too much impedance distorts the USB 2.0 eye pattern Source: TDC Corporation BSF-B02E

10 INSERTION LOSS CLCULTION Z Z F U 1 U 2 Z B Source Coupling way Load System attenuation Impedance = 20 log Z + Z + Z F B Z + Z B Z F = B ( ) ( ) Z + Z Z Z B in (db) in (Ω) The logarithmic ratio of input power to output power, which describes the signal attenuation along a defined transmission patch. The signal path could be a micro stip. 10

11 INSERTION LOSS CLCULTION 11

12 INSERTION LOSS CLCULTION 1 Ω Ground plane 10 Ω Supply voltage line 50 Ω - 90 Ω Data signal lines 12

13 INSERTION LOSS CLCULTION 13

14 INSERTION LOSS CLCULTION Z Z Z F F F = = = Ω ( Z + Z ) ( Z + Z ) ( ) ( ) B B B B 1. Require 12dB of attenuation at 125 MHz 2. Know that it is a power cable 3. Power port has 10 Ω impedance 4. Result is a impedance of 60 Ω Z = 20 log 10 = 20 log = db + Z Z = 20 log F Z + Z B F 10 B + 10 B B 14

15 INSERTION LOSS CLCULTION 1. 1.Require 12dB of attenuation at 125 MHz 2. Know that it is a power cable 12dB 3. Power port has 10 Ω impedance 4. Result is a impedance of 60 Ω 60Ω 15

16 Other components to consider Same function as a chip bead ferrite Different sizes and turn counts needed for application driven devices. ll used as a devices to attenuate high frequency noise. 16

17 Selecting the right feritte How do I know what s the best ferrite bead for me? PPLICTION To chose the proper bead, you should consider the following: Frequency range of the noise Source of noise mount of attenuation needed Environmental and electrical parameters of the circuit (not covert in this presentation) mbient temperature DC bias current Maximum operating current Frequency of the useful signal Real estate 17

18 CHOOSING CBF USING COMPONENT SELECTOR 18

19 CHOOSING CBF USING COMPONENT SELECTOR Step 1: Having impedance given frequency of noise, click on add own frequency button to visualize the table desired frequency (eg: 125Mhz) 19

20 CHOOSING CBF USING COMPONENT SELECTOR Step 2: Filtering with Impedance Ohm header column cell, the impedance range 20

21 CHOOSING CBF USING COMPONENT SELECTOR Step 3: Filtering with the IDC embedded filter dialog box the current values or range 21

22 CHOOSING CBF USING COMPONENT SELECTOR Step 4: Select the size, RDC, ect 22

23 CHOOSING CBF USING COMPONENT SELECTOR Click on the highlighted box to see the graph 23

24 CHOOSING CBF USING COMPONENT SELECTOR It s possible to use the dd filter button as alternative to step 1 and 2 24

Multilayer ferrites with in-rush current capability

Multilayer ferrites with in-rush current capability Alex Snijder Field Application Engineer Wurth Elektronik Nederland BV Alex.snijder@we-online.com AGENDA SMT chip bead ferrites Impedance Application