current sensing when accurate current sensing is required, a low value resistor is commonly used to generate a voltage proportional to the output current. the introduction of such a current sense resistor increases the circuit losses along with overall converter size and cost. using an output inductor with a tight dcr tolerance will eliminate the need for the current sense resistor. figure 2 ? inductor current sensing circuit the trend in modern power conversion is for high power density, reduced volume and increased efficiency. the drive for smaller, more efficient solutions presents a number of challenges for circuit design and component selection. inductor selection in high current core power applications is based on a need for high peak current ratings and low high frequency losses. these two requirements lead designers in different directions resulting in a compromise solution. designers are forced to select low inductance values to reduce inductor size (and ensure fast transient responses which results in high ripple currents needing to be absorbed by the inductor increasing losses) or select higher inductance values to reduce the ripple current and losses - but at a sacrifice of inductor size, efficiency and transient responses. the material of choice for core power multi-phase uncoupled inductors is ferrite. core power applications require a high saturation, high frequency, low loss, wide temperature range ferrite material to be selected. the reduced core loss at high frequency (coupled with a very low direct current resistance - dcr - single turn rectangular conductor) ensures high efficiency (see figure 1). high frequency inductors for core power applications r r l l c s + - coiltronics? inductor coiltronics? inductor coiltronics? inductor driver driver driver v in pwm sense sense sense pwm pwm q q q q q q micro- processor load r r r l l l c + c + c + figure 1 -typical three-phase voltage regulator module (vrm) figure 2 shows a typical inductor current sense circuit, where the voltage across c s is equal to the volt drop across the inductor dcr when the rc time constant is equal to the inductor time constant (r*c=l/r i ). the low dc resistance at tight tolerance enables the inductor to also function as a current sensor (dcr sensing). the cooper bussmann coiltronics ? flat-pac? series of inductors offers the largest variety of sizes, ratings, dcr options and stands out as the industry leader in multi-phase uncoupled core power applications. comparing the performance of traditional ferrite inductors (such as the fp2 with the new dcr current sense inductors from cooper bussmann) it can be seen that the benefits go beyond the elimination of sensing resistors.
from table 1 it can be seen that in addition to offering three different dcr values and tolerances the fp0705 has better performance over the traditional fp2 inductor. the fp0705 also has greater core loss stability over a wide temperature range, which is a consideration that is often overlooked during converter design. almost all inductor specifications show room temperature values. however, the effects of increased temperature need to be accounted for as peak current ratings are reduced and losses increased at elevated temperatures. the cooper bussmann coiltronics ? flat-pac? series of dcr current sensing inductors is available in footprints of 7 x 7mm, 7 x 8mm, 10 x 7mm, 10 x 8mm and 11 x 8mm with many inductance value c c o o i i l l t t r r o o n n i i c c s s c c o o r r e e n n o o m m i i n n a a l l i i r r m m s s i i p p k k d d c c r r c c o o r r e e l l o o s s s s h h e e i i g g h h t t p p a a r r t t n n o o . . m m a a t t e e r r i i a a l l i i n n d d u u c c t t a a n n c c e e ( ( a a ) ) 1 1 ( ( a a ) ) 2 2 ( ( m m ) ) ( ( m m w w ) ) 3 3 ( ( m m m m ) ) fp2-v150-r ferrite 150nh 37 23 0.28 50 5 fp0705r1-r15-r ferrite 150nh 43 30 0.25 10% 10 5 fp0705r2-r15-r ferrite 150nh 38 30 0.32 9.4% 10 5 fp0705r3-r15-r ferrite 150nh 32 30 0.46 6.5% 10 5 1. dc current for an approximate t of 40c 2. peak current for approximately 20% roll off at 25c 3. losses at 500khz, applied volt-second of 0.75v-s table 2 - high frequency inductor selection matrix table 1 ? dcr current sense inductor performance ranges and dcr tolerances. all parts exhibit low dcr, high peak current ratings and very low high frequency core losses that remain stable over a wide temperature range. the flat-pac? inductors are also rohs compliant and halogen free. the combination of these characteristics make the new flat-pac? inductors ideal for high frequency, high efficiency voltage regulation modules used in computer core power applications. see table 2 for a detail reference of the new core power inductor solutions available from cooper bussmann. i nductor coiltronics dimension ocl i sat (a)@ i rms (a) xx 1 = dcr(m ) xx 1 = series part number (mm) (nh) 25c 125c r1 r2 r3 r1 r2 r3 fp0705xx-r07-r 7 x 7 x 4.95 72 65 50 43 38 32 0.2510% 0.329.4% 0.466.5% fp0705xx-r10-r 7 x 7 x 4.95 105 44 36 43 38 32 0.2510% 0.329.4% 0.466.5% fp0705 fp0705xx-r12-r 7 x 7 x 4.95 120 37 30 43 38 32 0.2510% 0.329.4% 0.466.5% fp0705xx-r15-r 7 x 7 x 4.95 150 30 24 43 38 32 0.2510% 0.329.4% 0.466.5% fp0705xx-r18-r 7 x 7 x 4.95 180 25 20 43 38 32 0.2510% 0.329.4% 0.466.5% fp0705xx-r22-r 7 x 7 x 4.95 220 20 16 43 38 32 0.2510% 0.329.4% 0.466.5% fp0708xx-r07-r 8.5 x 7.0 x 7.2 72 90 72 44 - - 0.358.6% - - fp0708xx-r09-r 8.5 x 7.0 x 7.2 90 75 60 44 - - 0.358.6% - - fp0708 fp0708xx-r10-r 8.5 x 7.0 x 7.2 105 68 54 44 - - 0.358.6% - - fp0708xx-r12-r 8.5 x 7.0 x 7.2 120 59 47 44 - - 0.358.6% - - fp0708xx-r15-r 8.5 x 7.0 x 7.2 150 47 37 44 - - 0.358.6% - - fp0708xx-r19-r 8.5 x 7.0 x 7.2 190 37 29 44 - - 0.358.6% - - fp0805xx-r03-r 7.49 x 7.62 x 4.96 32 110 95 65 - - 0.1717% - - fp0805xx-r06-r 7.49 x 7.62 x 4.96 58 83 61 65 - - 0.1717% - - fp0805 fp0805xx-r07-r 7.49 x 7.62 x 4.96 72 67 49 65 - - 0.1717% - - fp0805xx-r10-r 7.49 x 7.62 x 4.96 100 50 35 65 - - 0.1717% - - fp0805xx-r20-r 7.49 x 7.62 x 4.96 200 20 16 65 - - 0.1717% - - fp0807xx-r07-r 7.4 x 7.6 x 7.0 70 108 79 49 - - 0.506% - - fp0807xx-r10-r 7.4 x 7.6 x 7.0 100 77 55 49 - - 0.506% - - fp0807xx-r12-r 7.4 x 7.6 x 7.0 120 66 48 49 - - 0.506% - - fp0807 fp0807xx-r16-r 7.4 x 7.6 x 7.0 160 48 36 49 - - 0.506% - - fp0807xx-r18-r 7.4 x 7.6 x 7.0 180 42 32 49 - - 0.506% - - fp0807xx-r20-r 7.4 x 7.6 x 7.0 200 38 28 49 - - 0.506% - - fp0807xx-r22-r 7.4 x 7.6 x 7.0 220 35 25 49 - - 0.506% - - 1. dcr indicator.
? 2008 cooper bussmann st. louis, mo 63178 636-394-2877 www.cooperbussmann.com reorder # 4038 1008 pdf only the cooper bussmann coiltronics ? brand of magnetics specializes in standard and custom solutions, offering the latest in state-of-the-art low-profile high power density magnetic components. we remain at the forefront of innovation and new technology to deliver the o ptimal mix of packaging, high efficiency and unbeatable relia bility. our designs utilize high frequency, low core loss materials, and new and cus tom core shapes in combination with innovative construction and packaging to provide designers with the highest performance parts available on the market. the coiltronics brand product line of power magnetics continually expands to satisfy shifts in technology and related market needs. standard product categories include: ? shielded drum inductors ? unshielded drum inductors ? high current inductors ? toroidal inductors ? specialty magnetics ? custom magnetics please visit http://www .cooperbussmann.com/da tasheets/elx to see data sheets on the wide variety of inductor solutions we have to offer. for techncial inquiries e-mail inductort ech@cooperindustries.com . order samples online - www .cooperbussmann.com table 2 - high frequency inductor selection matrix (continued) i nductor coiltronics dimension ocl i sat (a) @ i rms (a) xx 1 = dcr(m ) xx 1 = series part number (mm) (nh) 25c 125c r1 r2 r3 r1 r2 r3 fp1105xx-r10-r 8 x 11 x 4.9 100 81 63 46 - - 0.35 8.6% - - fp1105xx-r12-r 8 x 11 x 4.9 120 66 50 46 - - 0.35 8.6% - - fp1105 fp1105xx-r15-r 8 x 11 x 4.9 150 54 42 46 - - 0.35 8.6% - - fp1105xx-r20-r 8 x 11 x 4.9 192 42 34 46 - - 0.35 8.6% - - fp1105xx-r22-r 8 x 11 x 4.9 226 39 28 46 - - 0.35 8.6% - - fp1107xx-r07-r 7.2 x 11 x 7.2 70 140 123 55 42 - 0.29 10.0% 0.47 6.4% - fp1107xx-r12-r 7.2 x 11 x 7.2 120 90 72 55 42 - 0.29 10.0% 0.47 6.4% - fp1107xx-r15-r 7.2 x 11 x 7.2 150 70 56 55 42 - 0.29 10.0% 0.47 6.4% - fp1107 fp1107xx-r23-r 7.2 x 11 x 7.2 230 45 36 55 42 - 0.29 10.0% 0.47 6.4% - fp1107xx-r30-r 7.2 x 11 x 7.2 300 35 28 55 42 - 0.29 10.0% 0.47 6.4% - fp1107xx-r40-r 7.2 x 11 x 7.2 400 25 20 55 42 - 0.29 10.0% 0.47 6.4% - fp1107xx-r51-r 7.2 x 11 x 7.2 510 18 14.5 55 42 - 0.29 10.0% 0.47 6.4% - fp1005xx-r08-r 7 x 10.2 x 4.95 85 90 64 53 50 45 0.397.7% 0.476.7% 0.555.4% fp1005xx-r10-r 7 x 10.2 x 4.95 100 73 57 53 50 45 0.397.7% 0.476.7% 0.555.4% fp1005 fp1005xx-r12-r 7 x 10.2 x 4.95 120 60 48 53 50 45 0.397.7% 0.476.7% 0.555.4% fp1005xx-r15-r 7 x 10.2 x 4.95 150 47 37 53 50 45 0.397.7% 0.476.7% 0.555.4% fp1005xx-r22-r 7 x 10.2 x 4.95 220 33 26 53 50 45 0.397.7% 0.476.7% 0.555.4% fp1006xx-r08-r 8 x 10.2 x 6 85 100 70 53 45 - 0.27 12% 0.36 8.6% - fp1006xx-r10-r 8 x 10.2 x 6 100 85 64 53 45 - 0.27 12% 0.36 8.6% - fp1006 fp1006xx-r12-r 8 x 10.2 x 6 120 71 53 53 45 - 0.27 12% 0.36 8.6% - fp1006xx-r16-r 8 x 10.2 x 6 160 55 40 53 45 - 0.27 12% 0.36 8.6% - fp1006xx-r22-r 8 x 10.2 x 6 220 38 28 53 45 - 0.27 12% 0.36 8.6% - fp1007xx-r12-r 10.41 x 8 x 7.0 120 81 65 60 51 - 0.29 10% 0.48 8% - fp1007xx-r14-r 10.41 x 8 x 7.0 140 72 56 60 51 - 0.29 10% 0.48 8% - fp1007 fp1007xx-r17-r 10.41 x 8 x 7.0 170 58 46 60 51 - 0.29 10% 0.48 8% - fp1007xx-r22-r 10.41 x 8 x 7.0 215 50 36 60 51 - 0.29 10% 0.48 8% - fp1007xx-r30-r 10.41 x 8 x 7.0 300 32 26 60 51 - 0.29 10% 0.48 8% - 1. dcr indicator.
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