SMD Ferrite Selection lex Snijder Field pplication Engineer Wurth Electronik Nederland BV lex.snijder@we-online.com December 2014 LED EVENT s-hertogenbosch
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
The Würth Group strong family 3
The Würth Elektronik Group 4
Globally available. Locally present. 5
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
CBF DETILS General use High frequency 7
LOSSES 60 50 40 30 Inductors 1. pplication: Storage inductor 1. Request: Lowest possible core losses at switching frequency (HIGH Q) 20 10 0 1 10 100 1000 10/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. M 40 Ohm @ 240 MHz D.M. 120 Ohm @ 100 MHz Too much impedance distorts the USB 2.0 eye pattern Source: TDC Corporation BSF-B02E 2004.6 9
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 = 10 20 + 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
INSERTION LOSS CLCULTION 11
INSERTION LOSS CLCULTION 1 Ω Ground plane 10 Ω Supply voltage line 50 Ω - 90 Ω Data signal lines 12
INSERTION LOSS CLCULTION 13
INSERTION LOSS CLCULTION Z Z Z F F F = = = 10 10 20 12 20 59.6Ω ( Z + Z ) ( Z + Z ) ( 10 + 10 ) ( 10 + 10 ) 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 = 11.99 db + Z Z = 20 log 3.98 10 + F Z + Z B + 59.6 + F 10 B + 10 B B 14
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
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
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
CHOOSING CBF USING COMPONENT SELECTOR 18
CHOOSING CBF USING COMPONENT SELECTOR Step 1: Having impedance value @ given frequency of noise, click on add own frequency button to visualize the table column @ desired frequency (eg: 125Mhz) 19
CHOOSING CBF USING COMPONENT SELECTOR Step 2: Filtering with Impedance Ohm header column cell, the impedance range 20
CHOOSING CBF USING COMPONENT SELECTOR Step 3: Filtering with the IDC embedded filter dialog box the current values or range 21
CHOOSING CBF USING COMPONENT SELECTOR Step 4: Select the size, RDC, ect 22
CHOOSING CBF USING COMPONENT SELECTOR Click on the highlighted box to see the graph 23
CHOOSING CBF USING COMPONENT SELECTOR It s possible to use the dd filter button as alternative to step 1 and 2 24