Accessories Filter & Ring Core Chokes FP, L and LP Series Description These Filters and chokes are designed to reduce input in- terference and/or output ripple voltages occurring in appli- cations with switched mode power supplies. Since all our filters contain a Moly Permalloy Powder (MPP) ring core they feature very low DC losses as well as high DC mag- netisation and operate perfectly at the input and/or output of switching regulators ensuring effective filtering even at elevated DC current levels. These special characteristics allow the chokes to be operated at DC currents which con- siderably exceed the rated current, by accepting a corre- sponding gradual loss of inductance (unlike ferrite core chokes where inductance rapidly decreases above a cer- tain DC magnetising level). In applications where switching regulators have long supply lines, filters and chokes are used in order to prevent oscilla- tions caused by their negative input impedance. For further information refer also to switching regulator data for "Option L", and to section: Technical Information: Installation & Ap- plication. Table 1a: Type survey of FP filter blocks Table 1b: Type survey ring core chokes Filter type Matching switching Type Inductivity I Single Symm. Ln Part No. regulator type Part No. coil coil FP38 PSR 54 LP34-3 34 µH3 A • PSA 55 L20-7 20 µH7 A  PSA 5A2 LP20-7 20 µH7 A  PSA 5A5 PSA 123 LP183 2 ∞ 183 µH8 A  PSA 153 FP80 PSR 53 PSR 122.5 PSR 152.5 PSR 242 PSR 362 PSA 242.5 FP144 PSA 121.5 PSA 151.5 PSA 241.5 PSA 361 PSA 481 Filter Blocks FP Types The filter blocks contain, in addition to a MPP ring core, a interference voltages and currents, specially designed for capacitor and an attenuation resistor, capable of handling use in PCB applications together with switching regulators the high ripple currents seen at the input of switching regu- in an A01 case size. For selection of filters refer to the type lators. This forms a complete external filter system opti- survey. mised to prevent oscillations and to reduce superimposed Table of Contents Page Page Description ....................................................................... 1 Low-Loss Ring Core Chokes L/LP-Series ....................... 3 Filter Blocks FP Types ..................................................... 1 Mechanical Dimensions ................................................... 5 REV. SEP 29, 2003 Page 1 of 5 Accessories Filter & Ring Core Chokes FP, L and LP Series Electrical Data Filter Blocks General Condition: T = 25°C unless otherwise specified A Table 2: Filter blocks FP Characteristics Conditions FP38 FP80 FP144 min typ max min typ max min typ max Unit I Rated current L = 0.75 L 44 2 A DC Fn o U Rated voltage T ...T 5 40 5 80 15 144 V DC Fn C min C max R Ohmic resistance 18 20 22 18 20 22 90 95 100 mý F L No load inductance I = 0, T ...T 30 34 38 30 34 38 88 100 112 µH o L C min C max T Ambient temperature I = I –40 80 –40 80 –40 95 °C A F Fn T Case temperature –40 92 –40 92 –40 98 C T Storage temperature –40 100 –40 100 –55 100 S 2 2 For currents I > 4 A the following derating takes place: T = 100 – 1.3  I [°C], T = 100 – 0.49  I [°C] F A max F C max F Reduction of Output Ripple Input Interference Reduction An AC ripple current can be measured at the input of any Even though switching regulators have an inherently low switching regulator, even if they are equipped with an input output ripple, certain sensitive applications need even fur- filter. Depending on the types of filters used, common and/ ther reduction. In such cases, the filters designed to reduce disturbances at the input, can also be used for reducing the or differential mode interferences can be reduced. They will ripple on the output voltage (even better results with regard also help to further increase the surge and burst immunity of the power supplies. to the ripple and dynamic control deviation can be achieved by using low-loss ring core chokes in combination with an The FP filters considerably increase the source impedance external capacitor, see below). of the regulators superimposed interference, to a value The output ripple can be reduced by the use of filter blocks which is normally high in comparison to the impedance of the source (Z ). The interference currents are therefore by about 24 dB. The formula for the ripple u at the load R R L Line practically independent of their source impedance. The fil- is as follows: ter will reduce these currents by approximately 25 dB at a u = 0.063  u R o frequency of 150 kHz. (Ripple voltage u is given for specific regulators in the cor- o The interference voltages at the filter input are due to the responding data section). remaining interference currents flowing through the source Uii Uio impedance. The resulting interference voltage reduction 12010 Vi+ Vo+ Filter can be seen in the following figure. For frequencies above the regulator switching frequency the attenuation will in- U U U R Gi R PSR o L crease (up to 2 MHz approx.). Gi– Go– Parallel operation: When several switching regulator inputs are connected in parallel, each regulator should be Fig. 2 equipped with a separate input filter. Interconnections Reduction of voltage interference by FP filters should only be made in front of the filter or at its input Uii (i. e. the central ground point should be before or at the filter and under no circumstances at the regulator input). Consider, that the filter not only affects the output ripple but can also influence the voltage across the load R in the L inductive event of load changes. The static load regulation increases Att. [dB] resistive with the ohmic resistance of the choke i.e. 24 mV/A for the capacitive 12009 40 FP 38 and FP 80 filters and 95 mV/A for the FP 144 filter. 30 20 10 0 Z [ ] Line Fig. 1 0 1 2 3 4 5 6 Interference voltage reduction with FP filters at f = 150 kHz Source impedance REV. SEP 29, 2003 Page 2 of 5 Interference voltage reduction Accessories Filter & Ring Core Chokes FP, L and LP Series Typical Application The example in figure Reduction of voltage interference by 2. This example shows, that with an inductive source im- FP filters shows a switching regulator operating from a bat- pedance of 3.8 Ω, the insertion of the filter results in an tery (R < 0.5 Ω) with long supply lines (e.g. 2 m). The result- interference voltage reduction of approx. 18 dB (see i ing superimposed interference voltage U may be meas- fig.: Interference voltage reduction with FP filters at f = SL ured at the regulators input. The connection of a filter in 150 kHz). front of the power supply will reduce this interference ac- 3. The original superimposed interference voltage will be cordingly: reduced by a factor of approx. 8: 1. The regulator's source impedance is mainly inductive –18/20 U = U  10 [V] SF SL because of the low battery impedance and the long sup- 2  l ply lines. It can be calculated as follows: Uii Uio 12011 Vi+ Vo+ l Z l ≅ 2 π  f  L  2 l Filter Line S Line 3 -6 l Z l ≅ 2 π  (150  10 )  10  2  2 ≅ 3.8 Ω Line U Z R U U s Line Gi PSR o L f : Switching frequency (150 kHz) S Gi– Go– L : Supply line inductance (typically 1µH/m) Line l: Length of single supply line (twice for posi- Fig. 3 Reduction of voltage interference by FP filters tive and negative path) Low-Loss Ring Core Chokes L/LP-Series L /L [%] The ring core chokes, in combination with a capacitor, may o 12012 easily be used for application specific LC filters at the input 100 or output of switched mode power supplies. All chokes are LP183 suitable for PCB mounting. They are either moulded into 80 plastic cases or isolated from the PCB by means of an iso- 75 lation pad. LP34-3 60 Series L/LP20-7 and LP34-3 are intended for use as differ- L/LP20-7 ential mode filters and the current compensated choke LP183 enables attenuation of common mode interference. 40 20 Fig. 4 Choke inductance versus current 0 I [A] L 02 341 6 7 8 102 14 Electrical Data Ring Core Chokes General Condition: T = 25°C unless otherwise specified A Table 3: Ring core chokes Characteristics Conditions L20-7/LP 20-7 LP34-3 LP183 min typ max min typ max min typ max Unit 1 I Rated current L = 0.75 L 7 3 8 A DC Ln o R Ohmic resistance 5 5.5 6 18 20 22 2×2.9 2×4.2 2×5.5 mý L L No load inductance I = 0, T ...T 18 20 22 30 34 38 2×95 2×183 2×245 µH o L C min C max 2 D Current specific case 0.082 0.68 0.19 K/A TI 1 temp. increase 1 T Amb. temperature I = I –40 106 –40 104 –40 98 °C A L Ln T Case temperature –40 110 –40 110 –40 110 C T Storage temperature –40 110 –40 110 –40 110 S 1 If the choke is not operating at the rated current I , the maximum ambient temperature T and the maximum direct current I Ln A max L max change according to the following equations: T –T C max A max 2 I = T = T – I  D L max A max C max L max TI D TI REV. SEP 29, 2003 Page 3 of 5 I Ln I Ln Accessories Filter & Ring Core Chokes FP, L and LP Series Input Interference Reduction Reduction of Output Ripple Using L- or LP-series chokes together with an additional Even though switching regulators have an inherently low output ripple, certain sensitive applications need even fur- external capacitor a similar attenuation can be achieved as ther reduction. In such cases, the low-loss ring core chokes with filter blocks. The capacitor between the choke and the converter input is necessary in order to avoid possible oscil- designed to reduce disturbances at the input can also be lations caused by the negative input impedance of the regu- used for reducing the ripple on the output voltage. The lator. This phenomenon could cause the input voltage to chokes in combination with an external capacitor can achieve even better results than the Filter Blocks with re- leave the specified regulator input range. The relatively gard to the ripple and dynamic regulation. high ripple current flowing through the capacitor must be considered for the design. Refer also to: Technical Informa- The formula for the remaining output ripple at the load R is L tion: Installation & Application. calculated as follows: The current compensated choke LP183 has a high perme- U = u  Z /Z R o C ext LD ability ring core with two identical separate windings. The u : Output ripple of the regulator o normal operating current will only see the small stray in- Z : The impedance of the capacitor at the regu- Cex ductance between the windings. However common mode lator's switching frequency (150 kHz) corre- interference will be blocked by the full inductance of the sponds to the equivalent series resistance choke. (ESR) of the capacitor (please refer to the LP34-3 or LP183 L/LP20-7 corresponding data sheet). 12013 Vo+ Vi+ Z =2 π  f  L LD S D f : 150 kHz (regulator switching frequency) U S U PSR R o L Through the use of a common mode choke LP 183, the Gi– Go– common mode noise at the output can also be further re- C C C ext 1 ext 2 ext 3 duced. Fig. 5 Consider that the filter not only affects the output ripple but L/LP type chokes and capacitors used as input filter can also influence the voltage U across the load R in the R L event of load changes. The static regulation increases with Typical Application the ohmic resistance of the choke, i.e. 6 mV/A for the choke A voltage drop U = r  (I – I) is produced across the rGo Go o i L/LP20-7 and 20 mV/A for the LP34-3. ground loop resistance r . It is superimposed upon the Go The dynamic regulation is dependent on the size of the ca- regulators output voltage U and generates the voltage U o R pacitor. Generally, the bigger C the smaller is the dy- ex = U – U across the load resistance R . Without an input o r Go L namic, however, recovery will be slower. inductance L the current I in the input circuit has a rela- e i tively high AC component with a basic frequency f (regula- s R L Z Z D D LD C ext tor's switching frequency of approx. 150 kHz). This alternat- 12014 Vo+ Vi+ ing current produces an AC voltage component across r Go which is superimposed upon U . RL U U PSR U R R o L C To prevent this phenomenon, an inductance L can be in- e e serted into the input circuit. This causes the AC component Gi– Go– of the input current to be supplied entirely from the input capacitor C ; thus, I is a pure direct current. C should be e i e Fig. 7 wired as close as possible to the regulator's input terminals Low-loss ring core choke with external capacitor (C ex Vi+ and Gi–. approx. 1000 µF) used as output filter L and C additionally provide protection against input tran- e e sients and reduce radio interference voltages. External connection of Gi– and Go– or connection via a common ground is not recommended. The internal voltage drop U in the regulator would be superimposed on the rG output voltage. 12015 I o Vi+ Vo+ L e PSR U R U L U C e o RL U r G Gi– Go– r G Fig. 6 r Reduction of superimposed interference voltages in Go U r Go grounded power supply systems, caused by ground loops REV. SEP 29, 2003 Page 4 of 5 Accessories Filter & Ring Core Chokes FP, L and LP Series Mechanical Dimensions European Dimensions in mm. Tolerances ±0.2 mm unless otherwise specified Projection ±1 ±1 ±1 16.6 ±0.5 22 6.8 25 ø 3.8 4 3 min. 4.5 2 1 4 ±0.5 b b (3.22) 1 3.22 Legend: b = 5.08 mm 1 = Uii (input) 2 = Uio (output) 3 = Gi (ground) 0.8 4 = Positioning pins Fig. 8 27 Filter blocks FP weight 30 g 38.1 47.5 Fig. 9 M 2.5 Differential mode choke L20-7, weight 30 g ø 0.8 ø 1 max 8 ø 0.9 7.6 5.08 2 x 5.08 17.5 13.2 7.5 Fig. 10 Fig. 11 Differential mode choke LP34-3, weight 7 g Common mode choke LP183, weight 7 g NUCLEAR AND MEDICAL APPLICATIONS - Power-One products are not authorized for use as critical components in life support systems, equipment used in hazardous environments, or nuclear control systems without the express written consent of the respective divisional president of Power-One, Inc. TECHNICAL REVISIONS - The appearance of products, including safety agency certifications pictured on labels, may change depending on the date manufactured. Specifications are subject to change without notice. REV. SEP 29, 2003 Page 5 of 5 ±0.5 37.8 5.08 10 M 2.5 ±1 ø1.3 0.9 x 0.56 12018 1 ±1 5 (3.66) 3.66 10.16 b 15.24 12016 30 13.7 ±1 3.6 7.5 –0.5 3 max 14.5 6 12019 12017 4